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The age and diversification of terrestrial New World ecosystems through Cretaceous and Cenozoic time
Abstract
Eight ecosystems that were present in the Cretaceous about 100 Ma (million years ago) in the New World eventually developed into the 12 recognized for the modern Earth. Among the forcing mechanisms that drove biotic change during this interval was a decline in global temperatures toward the end of the Cretaceous, augmented by the asteroid impact at 65 Ma and drainage of seas from continental margins and interiors; separation of South America from Africa beginning in the south at ca. 120 Ma and progressing northward until completed 90-100 Ma; the possible emission of 1500 gigatons of methane and CO(2) attributed to explosive vents in the Norwegian Sea at ca. 55 Ma, resulting in a temperature rise of 5°-6°C in an already warm world; disruption of the North Atlantic land bridge at ca. 45 Ma at a time when temperatures were falling; rise of the Andes Mountains beginning at ca. 40 Ma; opening of the Drake Passage between South America and Antarctica at ca. 32 Ma with formation of the cold Humboldt at ca. 30 Ma; union of North and South America at ca. 3.5 Ma; and all within the overlay of evolutionary processes. These processes generated a sequence of elements (e.g., species growing in moist habitats within an overall dry environment; gallery forests), early versions (e.g., mangrove communities without Rhizophora until the middle Eocene), and essentially modern versions of present-day New World ecosystems. As a first approximation, the fossil record suggests that early versions of aquatic communities (in the sense of including a prominent angiosperm component) appeared early in the Middle to Late Cretaceous, the lowland neotropical rainforest at 64 Ma (well developed by 58-55 Ma), shrubland/chaparral-woodland-savanna and grasslands around the middle Miocene climatic optimum at ca. 15-13 Ma, deserts in the middle Miocene/early Pliocene at ca. 10 Ma, significant tundra at ca. 7-5 Ma, and alpine tundra (páramo) shortly thereafter when cooling temperatures were augmented by high elevations attained, for example, in the Andes<10 Ma and especially after 7-6 Ma.
... Our findings on the decrease in woodiness were in line with pollen records in East Asia (Barbolini et al., 2020) and the New World (Graham, 2011), which indicated that the proportion of pollens of woody plants has decreased since the early Eocene, whereas that of herbaceous plants has increased. We showed that herbaceous lineages had significantly higher speciation rates than woody lineages, whereas the extinction rates of the two growth forms were similar ( Figures S6 and S7). ...
... Typically, fossil records and reconstruction of the vegetation based on pollen profiles suggest that the rain forests in the New World (Graham, 2011) extended to the Arctic Circle during the Palaeocene. ...
... Fossil and pollen records suggest that with the decline in global temperature the tropical and subtropical evergreen broadleaf forests retreated, whereas grasslands and tundra expanded(Graham, 2011). Open tropical habitats (i.e., savannas), temperate grasslands and arctic and alpine ecosystems, including tundra, slowly developed and eventually became dominant over vast areas on different continents from the mid-Miocene (since 15 Ma) onwards(Graham, 2011). ...
Aim
Woody and herbaceous habits represent one of the most distinct contrasts among angiosperms, and the proportion of woody species in floras (i.e., “woodiness” hereafter) represents a fundamental structural element of plant diversity. Despite its core influence on ecosystem processes, spatio‐temporal patterns in woodiness remain poorly understood. Here, we aim to demonstrate the global spatio‐temporal patterns in angiosperm woodiness and their relationship with environmental factors.
Location
Global.
Time period
Cenozoic, 66 Ma to present.
Major taxa studied
Angiosperms.
Methods
Using newly compiled data on the growth forms and distributions of c . 300,000 angiosperm species and an angiosperm phylogeny, we mapped the current global geographical patterns in angiosperm woodiness, reconstructed ancestral states of growth forms through the angiosperm phylogeny and demonstrated the Cenozoic evolutionary dynamics of woodiness. We evaluated the relationships between woodiness and current climate and palaeoclimate.
Results
We found that c . 42.7% of angiosperms are woody. Woodiness decreased spatially from the equator towards high latitudes, temporally since the early Cenozoic. Temperature was the best predictor of the spatio‐temporal decline in woodiness and was positively correlated with woodiness. Despite the temporal decline in woodiness, macroevolutionary herbaceous‐to‐woody transitions increased through time and contributed to the evolution of woody floras in temperate drylands, whereas the opposite transitions decreased through time and contributed to herbaceous floras in tropical and subtropical drylands.
Main conclusions
Our study improves understanding of the spatio‐temporal dynamics of angiosperm woodiness. Our findings suggest that temperature is likely to be a determinant of spatio‐temporal variations in woodiness, highlighting the role of temperature in maintaining the growth form composition of ecosystems. Our study also calls for attention to growth form transitions (e.g., secondary woodiness) in temperate drylands that have been neglected before.
... In this sense, it has been proposed that primitive versions and essentially modern versions of the current Neotropical ecosystems were generated as a result of different processes that took place during the Cretaceous and the Cenozoic. A first approximation suggests that Neotropical lowland rainforests appeared 64 million years ago; while modern versions of scrub/chaparral, savannah and grassland emerged in the middle Miocene, approximately 13 to 15 million years ago (Graham 2011). ...
... It is possible that some of these elements have come from other continents, through different routes and at different times. For example, a group from Africa and Gondwana that probably entered the American continent from the north includes Acacia, Bursera, Caesalpinia, Cassia, Cedrela, Chrysophyllum, Ficus, Nectandra, Ocotea, Persea, Sapium, Sterculia and Terminalia (Burnham & Graham 1999;Graham 2011). ...
... The early Cenozoic floras from southern Central America contain few elements of dry habitats. However, by the Miocene-Pliocene boundary, these elements were multiplied, including 11 taxa (Poaceae, Acacia, Allophylus, Bursera, Cedrela, Ceiba, Combretum, Jatropha, Posoqueria and Pseudobombax) that collectively indicate an anticipated form of tropical dry forest (Burnham & Graham 1999;Graham 2011). ...
The chapter exposes the performance of Acacia melanoxylon wood for pulping production, regarding yields and kappa number but also the pulp and paper properties. The use of spectroscopy techniques is also emphasized.
... Floating and emergent aquatic angiosperms are common in two early-diverging orders-Nymphaeales (water lilies and allies) and Piperales (Friis et al., 2003)-as well as among the basal lineages of monocots and eudicots, which constitute the vast majority of extant crown-group angiosperms. The evolution of aquatic (submerged, emergent, and floating) angiosperms through the Cretaceous Period and early Cenozoic Era dramatically altered aquatic (littoral, limnetic) wetlands, which became essentially the same as modern forms by the Eocene Epoch of the Paleogene (Graham, 2011). ...
... During early Cenozoic "hothouse" climates, wetland floras at middle and high latitudes were dominated by taxodioid conifers (Cupressaceae) and deciduous broad-leaved eudicots, but palms extended to both the Arctic and Antarctic (Williams et al. 2003;Reichgelt et al., 2018). Freshwater marsh habitats became essentially modern in the Middle Eocene to Early Miocene (Graham, 2011). Through the mid-Miocene warm period (17-15 Ma) northern mid-latitude floras continued to include what are today more tropical as well as temperate lineages, but the latter came to dominate during the cooler late Neogene (Tiffney and Manchester, 2001). ...
... Through the mid-Miocene warm period (17-15 Ma) northern mid-latitude floras continued to include what are today more tropical as well as temperate lineages, but the latter came to dominate during the cooler late Neogene (Tiffney and Manchester, 2001). In North America, cool-temperate forests (and wetlands) at mid and high latitudes changed to boreal forests similar to their modern counterparts by the mid-Miocene (6 Ma) (Graham, 2011;Pound et al., 2012). Northern Hemisphere continental glaciation (waxing and waning) from the Pliocene (5 Ma) through the Quaternary was accompanied by dramatic changes in the distribution and extent of temperate and northern latitude wetlands as great ice sheets advanced and retreated across the continents. ...
Land plants first colonized, evolved, and diversified in wetlands. As plant stature and rooting systems evolved, so did the wetlands they inhabited: from groundcover wetlands, to marshes, to forest swamps on mineral substrates, and then to marshes (fens) and swamps on peat. The plants and animals that inhabited ancient wetlands were different from those of today, but as different types of wetlands evolved, so did their many critical functions and links to Earth's geochemical cycles. Herein we summarize the evolution of wetlands and key events in the prehistoric history of wetlands.
... Only a few records were documented from southern South America before the Barremian (Archangelsky and Seiler, 1980;Cornú, 1986). Later on, towards the beginning of the Aptian, the endorheic internal basins expanded and the wetlands occupied larger areas, some of them connecting to oceanic waters (Fig. 4C), while uplands remained restricted and of moderate height (Graham, 2011). These processes occurred concomitantly with greenhouse effects conditions, equable climates, high and uniform mean annual precipitation, and low thermal and biodiversity gradients (Föllmi, 2012;Hu et al., 2012;Graham, 2011). ...
... Later on, towards the beginning of the Aptian, the endorheic internal basins expanded and the wetlands occupied larger areas, some of them connecting to oceanic waters (Fig. 4C), while uplands remained restricted and of moderate height (Graham, 2011). These processes occurred concomitantly with greenhouse effects conditions, equable climates, high and uniform mean annual precipitation, and low thermal and biodiversity gradients (Föllmi, 2012;Hu et al., 2012;Graham, 2011). As a result of these dynamic physical and climatic conditions many taxa were widely distributed and numerous new habitats developed that probably contributed to the rapid evolution and establishment of aquatic ferns. ...
... Although aquatic and other freshwater or brackish habitats were present on Earth long before the Cretaceous, the concurrence in time and space of physical environmental factors (mainly climate changes and geological events) and the accessibility of lineages that could underwent evolutionary changes to exploit new opportunities would explain the diversification of the group during the Cretaceous. The same forcing mechanisms (Graham, 2011) could have promoted the post Paleocene water ferns decline as the new habitats were exploited by other evolving and more successful groups probably represented by several lineages within the flowering plants. ...
We compiled the fossil record of the heterosporous water ferns (Salviniales) including macro- and microfossils from South America and the Antarctic Peninsula. Both extant families, Marsileaceae and Salviniaceae, are well represented and several fossil spore genera that cannot be placed within the extant families are included as Incertae sedis. Marsileaceae is first recorded in the Middle to Late Jurassic. Incertae sedis genera are recorded for first time in the Early Cretaceous while Salviniaceae in the Late Cretaceous. Two diversity spikes are recognized: one spanned the Aptian–Albian (Early Cretaceous) and is linked to an increase in species diversity within Marsileaceae; and the other occurred during the Campanian–Maastrichtian (Late Cretaceous) and it is associated with the diversification at generic level of the entire Salviniales. Two decreases in diversity are recognized: one during the Cenomanian–Santonian and affected Marsileaceae at specific level but not its generic diversity, and the second is related to the Cretaceous–Paleogene mass extinction and affected all Salviniales at generic and specific levels. From the Paleocene onwards there is a steady decline in the fossil record of the group, with most remains belonging to the extant genera. This study suggests that Southern Hemisphere aquatic ferns underwent a sharp radiation during the Late Cretaceous and a deep decline in the Paleocene that parallels that occurred in the Northern Hemisphere. Probably, the temporal co-occurrence of geological and climate events and the availability of suitable lineages promoted the evolutionary changes of the water ferns in the studied area, including the high diversification and distribution in the Cretaceous and the subsequent post-Maastrichtian decline.
... Only a few records were documented from southern South America before the Barremian (Archangelsky and Seiler, 1980;Cornú, 1986). Later on, towards the beginning of the Aptian, the endorheic internal basins expanded and the wetlands occupied larger areas, some of them connecting to oceanic waters (Fig. 4C), while uplands remained restricted and of moderate height (Graham, 2011). These processes occurred concomitantly with greenhouse effects conditions, equable climates, high and uniform mean annual precipitation, and low thermal and biodiversity gradients (Föllmi, 2012;Hu et al., 2012;Graham, 2011). ...
... Later on, towards the beginning of the Aptian, the endorheic internal basins expanded and the wetlands occupied larger areas, some of them connecting to oceanic waters (Fig. 4C), while uplands remained restricted and of moderate height (Graham, 2011). These processes occurred concomitantly with greenhouse effects conditions, equable climates, high and uniform mean annual precipitation, and low thermal and biodiversity gradients (Föllmi, 2012;Hu et al., 2012;Graham, 2011). As a result of these dynamic physical and climatic conditions many taxa were widely distributed and numerous new habitats developed that probably contributed to the rapid evolution and establishment of aquatic ferns. ...
... Although aquatic and other freshwater or brackish habitats were present on Earth long before the Cretaceous, the concurrence in time and space of physical environmental factors (mainly climate changes and geological events) and the accessibility of lineages that could underwent evolutionary changes to exploit new opportunities would explain the diversification of the group during the Cretaceous. The same forcing mechanisms (Graham, 2011) could have promoted the post Paleocene water ferns decline as the new habitats were exploited by other evolving and more successful groups probably represented by several lineages within the flowering plants. ...
We describe a water fern spore assemblage from the Maastrichtian La Colonia Formation, Chubut Province, Patagonia, Argentina. The assemblage includes three species of Azolla (A. andreisii sp. nov., A. coloniensis, and A. sp. 1), two species of Azollopsis (A. intermedia and A. tomentosa), Crybelosporites pannuceus, Gabonisporis cristata, Ghoshispora sp., Grapnelispora loncochensis, two species of Molaspora (M. lobata and M. reticulata), and Paleoazolla patagonica. A. tomentosa, A. intermedia, G. cristata, and M. reticulata are recorded for the first time in the Southern Hemisphere. Ghoshispora sp. constitutes the southernmost record of the genus and its first mention for Argentina. In addition, the genus Azollopsis is emended to include megaspore apparatuses with more than one megaspore. This water fern spore assemblage is one of the most diverse so far known for South America and substantiates the significant radiation that aquatic ferns underwent worldwide at the end-Cretaceous. Furthermore, it also implies that the presence of widespread suitable paleoenvironments allowed the establishment and rapid evolution of these plant communities in Patagonia.
... The presence or absence of an endodermis with CBs in stems has been overlooked or deemphasized for a long time (see, e. g., Brebner, 1902;Dickison, 1975;Beck et al. 1982;Schmid 1982;Lersten, 1997;Gifford and Foster, 1989;Mauseth, 1988;Beck, 2010). Vascular tissues surrounded by an endodermis (monostely, polystely, or siphonostely) might be pleiosmorphic for some angiosperms, including major ANA grade basal angiosperms, monocots, and some groups of eudicots, even though these types of stem structure are undoubtedly derived in the vast majority of angiosperms because the aquatic/wetland plants which have them are considered to be derived from terrestrial ancestors (e.g., Arber, 1920;Sculthorpe, 1967;Cook, 1999;Cronk and Fennessey, 2001;Graham, 2011). Throughout the long history of the examination of angiospermous plants, there has been extremely scant evidence of an endodermis with demonstrable CBs in shoot tissues. ...
... Gomez et al. (2015) showed that the aquatic fossil Montsechia was closely related to Ceratophyllum, sister to the eudicots, as opposed to monocots (see questions raised by Soltis et al., 2018, and others). Further, Graham (2011) noted that aquatic habitats for early angiosperms were available long before many other kinds of habitats, and Gomez et al. (2015, page 10985) noted "some of the earliest angiosperms were fully aquatic very early in their ecological diversification". Soltis et al. (2018, page 33) went so far as to note that, because of the position of the members of the Nymphaeales, "the habit of the first angiosperms is reconstructed as equivocal". ...
... Thus, one might question what Cook (1999, page 79) stated: "The pioneer work by Arber (1920) and the thorough review by Sculthorpe (1967) have made it clear that all aquatic vascular plants have terrestrial ancestors." And, Graham (2011) noted the availabily of many kinds of habitats to early angiosperms. The fossil record and the ...
A sampling of angiosperms across a broad spectrum of families and generas was done to determine if angiosperms from the ANA grade basal angiosperms to the Zingiberales of the monocots and Apiales of the eudicots had an endodermis with demonstrable Casparian bands in shoots because the literature has a paucity of demonstrable images, especially for key basal plants. In the Amborellales, Amborella had no stem endodermis, but the aquatic Trithuria of the Nymphaeales had a monostele in which a layer endodermis enclosed its stem axial vascular tissues. Cabomba, Brasenia, and Nuphar of the Nymphaeales had polysteles in which an endodermis of distinct Casparian bands encircled each axial vascular bundle; Nymphaea had either an atactostele or a reduced polystele with only a few axial vascular bundles surrounded by endodermis. Among the magnoliids, Saururus and Houttuynia had monosteles with distinct endodermis Casparian bands. In many monocots, from Acorus, Acorales, to Thalia, Zingiberales, there was a monostele with an endodermis of Casparian bands surrounding a central cylinder of scattered axial vascular bundles. At the base of the eudicots, Ceratophyllum had a vascular core without endodermis. Some members of the Ranunuculales had stem endodermis in a polystelic arrangement. Nelumbo, Proteales, had a monostele of Casparian bands only in stolons. Unusual endodermal and vascular patterns, siphonosteles, were found in Gunnera, Gunnerales. Most eudicots with stem endodermis usually had a monostele or one endodermal layer of Casparian bands only surrounding one ring of vascular bundles, e. g., Myriophyllum, Drosera, Hippuris, Alternanthera, Lysimachia, and Hydrocotyle, but a polystele was present in Justicia. Some leaf petioles and lamina, e. g., Gunnera, Myriophyllum, Hippuris, and Hydrocotyle, had endodermis around their individual vascular bundles. While a stem endodermis was a distinct feature of aquatic or wetland plants, derived from terrestrial ancestors, the presence of stem endodermis by plants at the bases of some major angiosperm lines suggests that it may have been present early in angiosperm evolution.
... In the Oligocene, the epoch of origin of Myrcia, the Atlantic coast was covered by tropical rainforest (Morley, 2003), pointing to a likely origin of Myrcia on a tropical climate. After the mid-Miocene climatic optimum, the Earth experienced a cooling period (Graham, 2011) that together with the rising of Andes (Hoorn et al., 2010) ...
... legend; different colours over branches represent the most likely inherited range; colours over the tips of the phylogeny represent the current range of each species used in the ancestral reconstruction. Nodes with high support values (bootstrapping ≥70% and posterior probability ≥0.95) are identified with asterisks (following Amorim et al., 2019).(Graham, 2011;Hughes et al., 2013). It seems that the modification of climate and the origin of novel ecosystems in South America, such as savannas, have contributed to the diversification and specialization of some Myrcia sections in evoregion A. Current climate indicates that the main distinction between evoregions A and B is that A is colder and B ...
Aim
Myrcia is a plant genus exclusive of the Neotropical region and one of the most important components of the tree diversity in the Cerrado and Atlantic Forest domains. However, no mapping of its taxonomic diversity for this region exists. Our aim was to describe the spatial patterns of diversity and biogeographical history for Myrcia in the Neotropical region based on a phylogenetic regionalization.
Location
Neotropics.
Taxon
Genus Myrcia (Myrtaceae).
Methods
We derived distributions for 307 species from occurrence records using buffering and species distribution modelling. We used stacked distributions to generate a richness map of the genus and its clades (sections). In addition, we used phylogenetic regionalization methods to define evolutionary regions (evoregions) and ancestral area reconstruction to reveal the biogeographical history across these evoregions.
Results
We found high species richness in the Atlantic Forest and Cerrado, with some sections restricted to the East coast of South America, while others were widespread across the Neotropics. We defined five evoregions, named A–E; the ancestral reconstruction revealed that Myrcia originated in evoregion B, under a tropical climate, with further specialization of distant‐related lineages to the colder environmental condition in evoregion A.
Main Conclusions
High species richness of Myrcia in South America eastern coast and in the Brazilian highlands coincides with the evoregions with most diversification. Our genus‐specific regionalization together with the ancestral area reconstruction showed that evoregions A and B were the main evolutionary regions where diversification took place. In addition, the biogeographical history of the group suggests that some lineages have adaptations to deal with colder environments, that probably evolved in response to cooling periods since the mid‐Miocene.
... The global cooling of the Cenozoic, which was initiated at the early Eocene (~50 million years ago; Graham 2011, Condamine et al. 2012, created cold, dry climates (Graham 2011). Because ecological traits tend to be phylogenetically conserved (Latham and Ricklefs 1993b, Wiens and Donoghue 2004, Donoghue 2008, including those involved in surviving cold, dry climates Ricklefs 1993b, Donoghue 2008), the evolutionary breakthroughs allowing colonization of cold, dry environments have been limited to few tropical clades (Ricklefs 2006, Neves et al. 2021. ...
... The global cooling of the Cenozoic, which was initiated at the early Eocene (~50 million years ago; Graham 2011, Condamine et al. 2012, created cold, dry climates (Graham 2011). Because ecological traits tend to be phylogenetically conserved (Latham and Ricklefs 1993b, Wiens and Donoghue 2004, Donoghue 2008, including those involved in surviving cold, dry climates Ricklefs 1993b, Donoghue 2008), the evolutionary breakthroughs allowing colonization of cold, dry environments have been limited to few tropical clades (Ricklefs 2006, Neves et al. 2021. ...
The global cooling beginning in the Eocene has caused the coverage of tropical forests to contract from covering nearly all of Africa during the early Tertiary to about one tenth of Africa at the present time. Accompanying the climate cooling and drying was the evolution of traits tolerating cold and drought, particularly extreme drought in the Sahara. Here, we analyze a comprehensive data set of angiosperms to determine the effects of evolutionary history on assembly of angiosperms in regional floras in Africa. In particular, using phylogenetic metrics accounting for different depths of evolutionary history, we assess whether drought has caused stronger phylogenetic clustering relative to cold. We divided Africa into 27 regions, and collated species lists of angiosperms for each region. We used different phylogenetic metrics (tip‐ vs basal‐weighted) reflecting different evolutionary depths to quantify phylogenetic structure, and related phylogenetic structure metrics to climatic variables representing average, extreme and seasonality conditions of climate. Variations of phylogenetic structure across Africa were well explained by climate, with R² values being ~ 0.84 for each phylogenetic metric when all climatic variables used in this study were considered. Angiosperm assemblages with the strongest phylogenetic clustering are located in temperate regions, rather than in tropical desert regions of Africa. Minimum temperature explained much more variation in phylogenetic metrics than did minimum precipitation, suggesting that evolution of traits conferring cold tolerance is more phylogenetically constrained compared to those conferring drought tolerance. Temperature seasonality also explained much more variation in phylogenetic metrics than did precipitation seasonality. When mean annual temperature and precipitation are considered or when all temperature‐related variables and all precipitation‐related variables are considered, temperature variables are more important than precipitation variables in driving tip‐weighted phylogenetic structure of angiosperms in Africa but the pattern is reversed when basal‐weighted phylogenetic structure is considered.
... Crown-group Stenammini originated in the Holarctic during the Early Eocene approximately 51 Ma. This period corresponds to the early Eocene climatic optimum (EECO) when temperatures were roughly 12-16°C warmer than today (Westerhold et al., 2020;Zachos et al., 2001) and broad-leaved evergreen forest and paratropical rainforest were greatly expanded (Graham, 1993(Graham, , 2011. Fossil records indicate that broad-leaved, evergreen forest extended above 70°N latitude (Eberle & Greenwood, 2012;Harrington et al., 2012) and that relatives of animals with present-day tropical affinities, such as the tapir, inhabited these forests (Eberle & Greenwood, 2012). ...
... After the EECO there was a gradual decrease in global temperature culminating in a sharp decrease 33.9 Ma at the Eocene-Oligocene boundary. During the cooling, evergreen forests retracted, and more seasonal habitats expanded (Graham, 2011;Wing, 1987). This period is important because many modern plant and animal lineages originated (Bininda-Emonds et al., 2007;Jaramillo et al., 2010;Pellmyr & Leebens-Mack, 1999;Wing, 1987). ...
Aim
The standard latitudinal diversity gradient (LDG), in which species richness decreases from equator to pole, is a pervasive pattern observed in most organisms. Some lineages, however, exhibit inverse LDGs. Seemingly problematic, documenting and studying contrarian groups can advance understanding of LDGs generally. Here, we identify one such contrarian clade and use a historical approach to evaluate alternative hypotheses that might explain the group's atypical diversity pattern. We focus on the biogeographical conservatism hypothesis (BCH) and the diversification rate hypothesis (DRH).
Location
Global.
Taxon
Ants (Hymenoptera: Formicidae: Stenammini).
Methods
We examined the shape of the LDG in Stenammini by plotting latitudinal midpoints for all extant, described species. We inferred a robust genome‐scale phylogeny using UCE data. We estimated divergence dates using beast2 and tested several biogeographical models in BioGeoBEARS . To examine diversification rates and test for a correlation between rate and latitude, we used the programs BAMM and STRAPP, respectively.
Results
Stenammini has a skewed inverse LDG with a richness peak in the northern temperate zone. Phylogenomic analyses revealed five major clades and several instances of non‐monophyly among genera ( Goniomma , Aphaenogaster ). Stenammini and all its major lineages arose in the northern temperate zone. The tribe originated ~51 Ma during a climatic optimum and then diversified and dispersed southward as global climate cooled. Stenammini invaded the tropics at least seven times, but these events occurred more recently and were not linked with increased diversification. There is evidence for a diversification rate increase in Holarctic Aphaenogaster + Messor , but we found no significant correlation between latitude and diversification rate generally.
Main Conclusions
Our results largely support the BCH as an explanation for the inverse latitudinal gradient in Stenammini. The clade originated in the Holarctic and likely became more diverse there due to center‐of‐origin, time‐for‐speciation and niche conservatism effects, rather than latitudinal differences in diversification rate.
... Melodineae (I and II;30 spp.) and Hunterieae (20 spp.) remained restricted to the Paleotropics. Conversely, Amsonieae (16 spp.) shows a Laurasian distribution (North America, Europe, and Japan), possibly representing a relict component of the Eocene boreotropical flora, adapted to the cooler Neogene in higher latitudes and able to disperse through the Bering Strait, still available for subtropical plants during the late Miocene (Graham, 2011(Graham, , 2018. Alyxieae (138 spp.) dispersed to Southeast Asia and Oceania, reaching South America from the Paleotropics in the Eocene, Plumerieae (55 spp.) dispersed to South America in the Paleocene, showing independent diversifications in the New and Old Worlds since the late Eocene, and Carisseae (25 spp.) remained restricted to the Old World, with Carissa probably dispersing to Asia and Australia before the reduction of forests and expansion of grasslands, caused by an increase of aridity in northern and eastern India after the mid-Miocene climatic optimum (Chen et al., 2019). ...
... The dispersal of Asclepiadinae to North America in the late Miocene and subsequent diversification were likely favored by the expansion of grasslands in Africa and North America (Fishbein et al., 2011). The lineage would have reached North America through the Bering Strait (Rapini et al., 2007;Fishbein et al., 2011), which would have been available as a route for subtropical plants to the late Miocene (Graham, 2011(Graham, , 2018, suggesting that the lineage was present in Asia and became extinct during the cooler Quaternary, without leaving a trace of this dispersal route. After diversifying in North America, Asclepias dispersed to South America either by a stepping-stone route across the Central America Seaway (Rapini et al., 2007) or after the complete emergence of the Panama Isthmus and subsequent expansion of savannas (Bacon et al., 2016). ...
... Modern monocots are composed of 81 families and about 60.000 species. Their origin and rapid explosion is still under debate (Doyle 2006;2012 and references therein) but they became the significant components of the ecosystem from the Cretaceous (Friis et al. 2011).They changed the face of earth ecosystem and provided the structural definition for most terrestrial ecosystems (Crepet 2000;Graham 2011). The diversification of this group also assisted in the explosion of the ferns (Schneider et al. 2004) and co-evolution of the insects (Grimaldi & Engel 2005). ...
... The early fossil history of monocots is a subject of dispute (Doyle 1973;Gandolfo et al. 2000;Friis et al.2004;2011;Hofmann & Zetter 2010) and their report from the Early Cretaceous is uncertain (Gandolfo et al. 1998(Gandolfo et al. , 2000. However, recent studies establish their existence during the Early Cretaceous (Coiffard et al. 2019;Liu et al. 2020). ...
Reports of the angiosperm macrofossils from the Early Cretaceous sediments of India are relatively poor, with only one report from the Krishna-Godavari Basin. The present study documents a monocotyledon leaf fossil from the Barremian-Aptian (Early Cretaceous) of Gangapur Formation, Pranhita-Godavari Basin, India. The present fossil leaf placed under a new genus Sahniophyllum and it is characterised by the ribbon shaped leaves, with parallel venation, arranged in rosette form suggests its probable affinity with Hydrocharitaceae. The taphocoenosis demonstrates its autochthonous preservation and aquatic habitat.
Keywords:
Angiosperm; Early Cretaceous; Gangapur Formation; India; Monocot; Sahniophyllumindica gen. et sp. nov.
... Since the onset of global climate cooling in the early Eocene (c. 50 million years ago; Condamine et al., 2012;Graham, 2011), temperatures decreased faster at higher latitudes, increasing the gradient in temperature from the Equator to the poles (Qian et al., 2013). The Arctic biome, as we know it today, first appeared only 2-3 million years ago, during the late Pliocene, when the continuous Tertiary forests in the Arctic region across Eurasia and North America were replaced by tundra (Briggs, 2007;Murray, 1995). ...
... The dramatic cooling of the Earth's climate from the early Eocene (c. 50 million years ago; Condamine et al., 2012;Graham, 2011) to the Last Glacial Maximum (c. 18,000 years ago) precipitated a major distributional shift in vegetation. ...
Aim
The Arctic is the coldest inhabited region on Earth, and it supports few terrestrial species. The tropical‐climate origin of many angiosperm clades, along with strong phylogenetic niche conservatism, likely constrained colonization of cold environments for many plants. However, invasion of the Arctic by many lineages might also have opened up a new adaptive landscape that facilitated subsequent diversification. We might, therefore, expect species in this biome to be descendants of a few cold‐tolerant lineages. Here, we explore the assembly of the Arctic flora using data on the relationships and distributions of > 80,000 species.
Location
The Northern Hemisphere.
Time period
Current.
Taxon
Flowering plants.
Methods
The Arctic was divided into five bioclimate subzones. We assembled a species pool for flowering plants in the Northern Hemisphere, and determined which species of the species pool are distributed in the Arctic and each of its subzones. We used two metrics (the standardized effect sizes of mean pairwise distance and Faith’s phylogenetic diversity; MPD ses and PD ses , respectively) to quantify phylogenetic dispersion of flowering plant assemblages.
Results
When the Arctic species were compared to all the species in the Northern Hemisphere, MPD ses and PD ses were −12.85 and −27.17, respectively, indicating that the Arctic flora is a phylogenetically clustered subset of the Northern Hemisphere species pool. In general, MPD ses and PD ses decreased from the south to the north within the Arctic, indicating that some lineages are further filtered stepwise into more northerly Arctic subzones.
Main conclusions
The species of the Arctic flora comprise a phylogenetically clustered subset of the broader Northern Hemisphere flora. The more negative value for PD ses compared to MPD ses indicates that clustering is stronger towards the tips of the phylogenetic tree. We suggest that the majority of Arctic species are nested within clades having attributes that enabled adaptation to cold climates.
... Melodineae (I and II;30 spp.) and Hunterieae (20 spp.) remained restricted to the Paleotropics. Conversely, Amsonieae (16 spp.) shows a Laurasian distribution (North America, Europe, and Japan), possibly representing a relict component of the Eocene boreotropical flora, adapted to the cooler Neogene in higher latitudes and able to disperse through the Bering Strait, still available for subtropical plants during the late Miocene (Graham, 2011(Graham, , 2018. Alyxieae (138 spp.) dispersed to Southeast Asia and Oceania, reaching South America from the Paleotropics in the Eocene, Plumerieae (55 spp.) dispersed to South America in the Paleocene, showing independent diversifications in the New and Old Worlds since the late Eocene, and Carisseae (25 spp.) remained restricted to the Old World, with Carissa probably dispersing to Asia and Australia before the reduction of forests and expansion of grasslands, caused by an increase of aridity in northern and eastern India after the mid-Miocene climatic optimum (Chen et al., 2019). ...
... The dispersal of Asclepiadinae to North America in the late Miocene and subsequent diversification were likely favored by the expansion of grasslands in Africa and North America (Fishbein et al., 2011). The lineage would have reached North America through the Bering Strait (Rapini et al., 2007;Fishbein et al., 2011), which would have been available as a route for subtropical plants to the late Miocene (Graham, 2011(Graham, , 2018, suggesting that the lineage was present in Asia and became extinct during the cooler Quaternary, without leaving a trace of this dispersal route. After diversifying in North America, Asclepias dispersed to South America either by a stepping-stone route across the Central America Seaway (Rapini et al., 2007) or after the complete emergence of the Panama Isthmus and subsequent expansion of savannas (Bacon et al., 2016). ...
Apocynaceae (the dogbane and milkweed family) is one of the ten largest flowering plant families, with approximately 5,350 species and diverse morphology and ecology, ranging from large trees and lianas that are emblematic of tropical rainforests, to herbs in temperate grasslands, to succulents in dry, open landscapes, and to vines in a wide variety of habitats. Despite a specialized and conservative basic floral architecture, Apocynaceae are hyperdiverse in flower size, corolla shape, and especially derived floral morphological features. These are mainly associated with the development of corolline and/or staminal coronas and a spectrum of integration of floral structures culminating with the formation of a gynostegium and pollinaria—specialized pollen dispersal units. To date, no detailed analysis has been conducted to estimate the origin and diversification of this lineage in space and time. Here, we use the most comprehensive time-calibrated phylogeny of Apocynaceae, which includes approximately 20% of the species covering all major lineages, and information on species number and distributions obtained from the most up-to-date monograph of the family to investigate the biogeographical history of the lineage and its diversification dynamics. South America, Africa, and Southeast Asia (potentially including Oceania), were recovered as the most likely ancestral area of extant Apocynaceae diversity; this tropical climatic belt in the equatorial region retained the oldest extant lineages and these three tropical regions likely represent museums of the family. Africa was confirmed as the cradle of pollinia-bearing lineages and the main source of Apocynaceae intercontinental dispersals. We detected 12 shifts toward accelerated species diversification, of which 11 were in the APSA clade (apocynoids, Periplocoideae, Secamonoideae, and Asclepiadoideae), eight of these in the pollinia-bearing lineages and six within Asclepiadoideae. Wind-dispersed comose seeds, climbing growth form, and pollinia appeared sequentially within the APSA clade and probably work synergistically in the occupation of drier and cooler habitats. Overall, we hypothesize that temporal patterns in diversification of Apocynaceae was mainly shaped by a sequence of morphological innovations that conferred higher capacity to disperse and establish in seasonal, unstable, and open habitats, which have expanded since the Eocene-Oligocene climate transition.
... Most major clades of present-day terrestrial organisms first appeared when the climate of the Earth was warm and humid (e.g., during the Cretaceous and early Tertiary ;Behrensmeyer et al., 1992). Traits that confer cold or drought tolerance evolved only later, during the global climate cooling that started in the early Eocene (Graham, 2011). Owing to phylogenetic niche conservatism, many clades remain constrained to tropical conditions, with only occasional evolutionary breakthroughs into temperate conditions (Wiens & Donoghue, 2004). ...
... The contrasting patterns observed for gymnosperms and angiosperms might result, at least in part, from the fact that present-day distributions of many gymnosperm genera and species reflect remnants of their once broadly distributed populations before extinction during geological times, and their contemporary distributions might not reflect their ecological niches . Furthermore, because many families and most genera of angiosperms originated during global climate cooling initiated in the early Eocene, whereas all the families of gymnosperms originated long before global climate cooling (Graham, 2011;Smith & Brown, 2018;Zanne et al., 2014), the mechanisms associated with the TNC hypothesis might have played an important role in driving assembly of angiosperms but not of gymnosperms. ...
Aim
Previous studies have found strikingly different geographical patterns of phylogenetic diversity of gymnosperms and angiosperms, which have been suggested to result, in part, from the greater age of the former. To assess the effects of clade age on phylogenetic structure, we assessed phylodiversity patterns of pteridophytes (lycophytes and ferns), which combine ancient and modern lineages, across China.
Location
China.
Time period
Present day.
Taxon
Pteridophytes.
Methods
We divided China into 66 regions and collated species lists of pteridophytes for each region. We then related taxonomic and phylogenetic diversity, and their related metrics, to six climatic variables for pteridophytes as a whole and for different evolutionary clades. We examined the effect of spatial autocorrelation among regional floras on the results.
Results
We found that when all pteridophytes or ferns were considered, the patterns resembled those of gymnosperms, presumably reflecting the effects of several ancient global mass extinctions and the relict distribution of old families. In contrast, when we considered only the modern Polypodiales radiation, which accounts for three-quarters of current fern diversity and is about as old as the angiosperm radiation, we found a pattern similar to that of angiosperms. This pattern is consistent with the tropical niche conservatism hypothesis and suggests that both major groups of land plants have a broadly similar evolutionary trajectory, with most families originating in tropical conditions and few families adapting to cold and arid conditions.
Main conclusions
Our study shows that the phylogenetic structures of more recently evolved and diversified clades of pteridophytes are fairly consistent with the tropical niche conservatism hypothesis, suggesting that the age of the taxon, its physiological adaptations and the global climatic changes that it experienced during its evolutionary history are reflected in the composition of current plant assemblages.
... Conversely, hypotheses for a recent assembly propose diversification of endemic Cerrado taxa through adaptive habitat shifts from surrounding forest biomes likely triggered by suitable climate conditions and grassland expansion in South America (Antonelli et al., 2018;Simon et al., 2009;Souza-Neto et al., 2016). So far, most phylogenetic studies addressing the origin of savanna endemics (reviewed by Azevedo et al. (2020)) together with the pollen fossil record (Graham, 2011) support a recent species assembly in the Miocene (ranging from 21 to 10 MYA) compared to the much older assembly of the neighbouring rain forests in the Mid-Cretaceous (Davis et al., 2005). However, only few studies have evaluated the role of dispersal across contrasting biomes as an important process promoting the origin and accumulation of species diversity in different ecoregions in the Neotropics (Antonelli et al., 2018;Pinto-Ledezma et al., 2017;Zizka et al., 2020). ...
... Evolutionary predisposed adaptations may also play a strong role (Donoghue & Edwards, 2014). The Boana pulchella group might have some physiological tolerance to different climatic conditions and humidity levels that could predispose these treefrogs to recurrent habitat shifts, possibly moderated by the impact of past climate changes in southern South America (Graham, 2011). However, eco-physiological experiments would be necessary to confirm this possibility. ...
Aim
We investigate the biogeographical history and diversification in a treefrog lineage distributed in contrasting (open and forested) ecoregions of South America, including three biodiversity hotspots. We evaluate the role of dispersal and whether other factors such as diversity‐dependence or paleotemperatures could explain the diversification pattern for this group. Especially focusing on the savanna endemics, we illuminate the processes governing the species assembly and evolution of the Cerrado savanna.
Location
South American ecoregions south of the Amazon (i.e. Atlantic Forest, Cerrado, Araucaria Forest, Pampas, Central and Southern Andes).
Taxon
Boana pulchella group.
Methods
We built the most complete time‐calibrated phylogeny for the group to date. We then reconstructed ancestral ranges using the dispersal‐extinction‐cladogenesis (DEC) model comparing different dispersal scenarios considering distance, adjacency and ecological similarity among regions. Centre‐of‐origin hypotheses in forest and open ecoregions were also tested. Using biogeographical stochastic mapping, we additionally estimated the contribution of range shifts across different biomes. Lastly, we evaluated several diversification models, including the effect of time, diversity‐dependence and temperature‐dependence on speciation and extinction rates.
Results
The Boana pulchella group originated during the Early Miocene (~17.5 MYA) and underwent high speciation rates during the Middle Miocene Climatic Optimum, with a decreasing trend following the Miocene Climatic Transition. We found no support for a single ecoregion acting as a centre of origin and diversification; instead, we inferred recurrent range shifts with dispersal among dissimilar adjacent ecoregions. Speciation linearly dependent on paleotemperatures, with either no or very low constant extinction rates, best explained the slowdown diversification pattern.
Main conclusions
Our results support a species assembly of Cerrado savanna in South America during the Miocene with intermittent interchange with rain forest habitats. Past climate changes impacted the rate new species originated with apparently no impact on extinction. Finally, the repeated habitat shifts among open/dry and forested/humid ecoregions, rather than long‐term in‐situ diversification in single areas, highlights the very dynamic historical interchange between contrasting habitats in South America, possibly contributing to its high species diversity.
... There are several land bridges in particular that might have facilitated migration of the Millettioid/Phaseoloid clade across the Northern Hemisphere. The North Atlantic Land Bridge (NALB) and the Bering Land Bridge (BLB) represent major pathways for plant migration in the Northern Hemisphere that were available at different times throughout the Cenozoic (Tiffney, 1985;Graham, 2011;Zhou et al., 2012;van Welzen et al., 2014;Wen et al., 2016;Jabbour et al., 2018;Duan et al., 2021;Kramina et al., 2021). The Afro-Arabian plate is a landmass that may be important in facilitating dispersal between the African continent and Eurasia, resulting in modern disjunctions between Africa and Asia (Zhou et al., 2012). ...
The Millettioid/Phaseoloid (or the Millettioid) clade is a major lineage of the subfamily Papilionoideae (Fabaceae) that is poorly understood in terms of its diversification and biogeographic history. To fill this gap, we generated a time‐calibrated phylogeny for 749 species representing c . 80% of the genera of this clade using nrDNA ITS, plastid matK , and plastome sequence (including 38 newly sequenced plastomes). Using this phylogenetic framework, we explored the clade's temporal diversification and reconstructed its ancestral areas and dispersal events. Our phylogenetic analyses support the monophyly of the Millettioid/Phaseoloid clade and four of its tribal lineages (Abreae, Desmodieae, Indigofereae, and Psoraleeae), while two tribal lineages sensu lato millettioids and phaseoloids are polyphyletic. The fossil‐calibrated dating analysis showed a nearly simultaneous divergence between the stem node ( c . 62 Ma) and the crown node ( c . 61 Ma) of the Millettioid/Phaseoloid clade in the Paleocene. The biogeographic analysis suggested that the clade originated in Africa and dispersed to Asia, Europe, Australia, and the Americas at different periods in the Cenozoic. We found evidence for shifts in diversification rates across the phylogeny of the Millettioid/Phaseoloid clade throughout the Cenozoic, with a rapid increase in net diversification rates since c . 10 Ma. Possible explanations for the present‐day species richness and distribution of the Millettioid/Phaseoloid clade include boreotropical migration, frequent intra‐ and intercontinental long‐distance dispersals throughout the Cenozoic, and elevated speciation rates following the Mid‐Miocene Climatic Optimum. Together, these results provide novel insights into major diversification patterns of the Millettioid/Phaseoloid clade, setting the stage for future evolutionary research on this important legume clade.
... They diversified during the Cretaceous and Tertiary when equable conditions of warm (tropical) climate were widespread across the globe [5][6][7] . Temperatures decreased more quickly at higher latitudes during the global cooling initiated in the early Eocene 8,9 , so that the gradient of temperature from the equator to the poles became steeper as the time approached the Pleistocene, where cycles of glaciation forced tropical lineages at higher latitudes to withdraw to lower (warmer) latitudes or to evolve tolerance for colder temperatures unless they went extinct. Because ecological traits are phylogenetically conserved 10 and an evolutionary event can rarely produce a clade that is able to survive and reproduce in novel climatic conditions such as freezing temperatures 3,4,11,12 , relatively few clades have crossed the ecophysiological barrier into cold environments. ...
The tendency of species to retain ancestral ecological distributions (phylo-genetic niche conservatism) is thought to influence which species from a species pool can persist in a particular environment. Thus, investigating the relationships between measures of phylogenetic structure and environmental variables at a global scale can help understand the variation in species richness and phylogenetic structure in biological assemblages across the world. Here, we analyze a comprehensive data set including 341,846 species in 391 angiosperm floras worldwide to explore the relationships between measures of phylogenetic structure and environmental variables for angiosperms in regional floras across the world and for each of individual continental (bio-geographic) regions. We find that the global phylogenetic structure of angiosperms shows clear and meaningful relationships with environmental factors. Current climatic variables have the highest predictive power, especially on phylogenetic metrics reflecting recent evolutionary relationships that are also related to current environmental heterogeneity, presumably because this favors plant speciation in various ways. We also find evidence that past climatic conditions, and particularly refugial conditions, play an important role in determining the phylogenetic structure of regional floras. The relationships between environmental conditions and phylogenetic metrics differ between continents, reflecting the different evolutionary histories of their floras.
... Whereas geologic trends in terrestrial floral and faunal habitat ranges (76,77) and diversity (78)(79)(80) are largely thought to be controlled by temperature and associated climate patterns, atmospheric CO 2 has been hypothesized to drive the evolution of biological carbon-concentrating mechanisms (CCMs) and their subsequent diversification in terrestrial plants (Fig. 2D) (81,82). Our realization of how atmospheric CO 2 has varied through the Cenozoic allows us to reexamine this hypothesis. ...
The geological record encodes the relationship between climate and atmospheric carbon dioxide (CO 2 ) over long and short timescales, as well as potential drivers of evolutionary transitions. However, reconstructing CO 2 beyond direct measurements requires the use of paleoproxies and herein lies the challenge, as proxies differ in their assumptions, degree of understanding, and even reconstructed values. In this study, we critically evaluated, categorized, and integrated available proxies to create a high-fidelity and transparently constructed atmospheric CO 2 record spanning the past 66 million years. This newly constructed record provides clearer evidence for higher Earth system sensitivity in the past and for the role of CO 2 thresholds in biological and cryosphere evolution.
... If ancestral Q. suber populations experienced rapid growth before a single chloroplast lineage could be fixed throughout the entire species range, then the two haplogroups could have persisted without major constraints for long periods. Diversification in Quercus species has been related to ecological opportunity due to a mid-Miocene temperature decrease (Graham 2011;Hipp et al. 2020), which may have promoted population expansion as well as speciation. Large effective population sizes throughout the Miocene may have enabled the retention of different chloroplast lineages up to the Pleistocene, when glaciation cycles caused range contractions in tree species north of the Mediterranean, that affected Q. suber (López de Heredia et al. 2007a;Vessella et al. 2015). ...
Chloroplast genome diversity in cork oak (Quercus suber) is characterised by the occurrence of haplotypes that are akin to those found in other Mediterranean oak species, particularly in Q. ilex and Q. rotundifolia, suggesting the possible presence of an introgressed chloroplast lineage. To further investigate this pattern, we reconstructed chloroplast haplotypes by sequencing four chloroplast markers (cpDNA), sampled across 181 individuals and 10 taxa. Our analyses resulted in the identification of two diversified chloroplast haplogroups in Q. suber, corresponding to a geographically widespread lineage and an Afro-Iberian lineage. Time-calibrated phylogenetic analyses of cpDNA point to a Miocene origin of the two haplogroups in Q. suber, suggesting that the Afro-Iberian lineage was present in cork oak before the onset of glaciation periods. The persistence of the two haplogroups in the western part of the species distribution range may be a consequence of either ancient introgression events or chloroplast lineage sorting, combined with different fixation in refugia through glaciation periods. Our results provide a comprehensive insight on the origins of chloroplast diversity in these ecologically and economically important Mediterranean oaks.
... In the last couple of decades, a series of contributions have significantly improved our knowledge of the diversity and affinities of all major lineages of South American metatherians. It is not the purpose of this work to detail such diversity; instead, the following studies offer a general panorama on these topics (the list is not exhaustive and refers mostly to extinct taxa): "Ameridelphia," Horovitz et al. (2009), Oliveira and Goin (2006, 2011 Goin and Abello (2013), and Barmak et al. (2021). A detail of currently recognized families and orders of North and South American metatherians is given in Table 1. ...
... As a result of these complex effects, river capture has been implicated in the formation of high freshwater diversity in many regions and taxa (Albert et al. 2018a(Albert et al. , 2018b. Most of the ecosystems, clades and even species of Amazonian and in fact of many of Earth's ancient tropical biotas (e.g., Wiens & Donoghue 2004) are older than the geographic conditions in which they live today (Hoorn & Wesselingh 2010a, 2010bHoorn et al. 2010;Albert et al. 2011Albert et al. , 2018aGraham 2011). ...
Bujurquina is the most widely distributed and species-rich genus of cichlids in the western
Amazon of South America. In this study we describe a new species from Peru from a hypothesized
reverse flowing river system. Prior to the origin of the modern Amazon River at 4.5 Ma, this river system
had its headwaters on the Iquitos arch, one of several main structural arches (swells) in the Amazon.
Prior to the origin of the modern Amazon these arches formed topographic barriers of drainage basins
in lowland Amazonia. For our analyses we use morphological and molecular data, analyzed through
multivariate statistics and molecular phylogenies, respectivelly. For all valid species in the genus (except
B. cordemadi and B. pardus) we additionally for the first time provide photographs of live specimens.
Based on DNA phylogeny and coloration patterns we demonstrate that Bujurquina is divided into two
main clades and based on this we provide a dichotomous key for all the species.
... Pseudoclavellaria longiclava (Zhang, 1989) Zhang (1989, Taeger et al. (2010) Sinocimbex pellucidus Zhang et al., 1994Zhang et al. (1994 Sinocimbex silaceus Zhang et al., 1994Zhang et al. (1994 Highlands except the Dipsacaceae and Geraniaceae, and many genera of these families that are important today first appear there (e.g., Crane & Stockey 1987, Wolfe & Wehr 1987Wehr & Hopkins 1994;Greenwood et al. 2005;Moss et al. 2005;Devore & Pigg 2007Mathewes et al. 2016;Pigg & Devore 2016). The temperate montane Okanagan Highlands had a high diversity of insects and plants (woody dicots analysed) associated with climatic factors (Archibald et al. 2010), and may have been the setting for the origin of modern microthermal northern forests that the great majority of extant Cimbicidae prefer which later spread downslope into lowlands in the globally cooler Neogene (Graham 2011). ...
We erect the Cenocimbicinae, a new subfamily of Cimbicidae (Hymenoptera, Symphyta), restricted to the Selandian Menat Formation of France, the oldest occurrence of the family, and the Ypresian Okanagan Highlands of far-western North America. We describe new taxa from the Okanagan Highlands: Allenbycimbex morrisae gen. et sp. nov. and Leptostigma n. gen. with seven new species: L. alaemacula n. sp., L. brevilatum n. sp., L. fasciatum n. sp., L. longiclava n. sp., L. longipallidum n. sp., L. longitenebricum n. sp., and L. proxivena n. sp. We revise the Cimbicidae from the Ypresian Green River Formation and the Priabonian Florissant Formation, both in Colorado, USA. The oldest fossil of a modern cimbicid subfamily appears with a single pachylostictine specimen in the Green River Formation, and all Cimbicidae are in modern subfamilies after the Ypresian (we did not examine one larva known from Priabonian Baltic amber). Pseudocimbex clavatus Rohwer 1908 from the Florissant Formation is not a cimbicid; we treat it as Tenthredinoidea incertae sedis. We transfer Cimbex vetusculus Cockerell to Floricimbex n. gen.
... Professor Alan Graham and his associates from the Missouri Botanical Garden, USA, carried out extensive palaeobotanical and palynological research on the late Cretaceous-Cenozoic sediments of the Caribbean Islands and Central America for almost four decades. Their pioneering contribution to the geological history of this region, Cenozoic floristic evolution, pollen and spore floras, climate and environmental changes of this vast region has been synthesized in Graham (2010Graham ( , 2011 that laid the foundation for future research. Graham (1995) stated that the mangrove community of the Neotropics shows a progressive increase in diversity through the Cenozoic. ...
Kumar A. 2023. Palynological research in the Caribbean Islands and Central America: An overview. Geophytology 53(1): 83-98.
There is rich literature on palynological research in the Caribbean Islands and the adjoining regions of Central America. However, these papers were published in a variety of diverse journals originating from several countries mainly in the Americas, Europe, and a few from the Caribbean countries as well. An overview of the palynological research in the Caribbean and the adjoining regions provides information on the diverse application of palynology in the Earth and Environmental Sciences. This study also provides a survey of significant papers useful to researchers in this field of science interested in initiating a research project in this region. However, some aspects of palynology such as Melissopalynology (study of pollen and spores in honey), Forensic Palynology (study of palynomorphs in Criminology), Entomopalynology (pollen studies in the body of insects) and study of pollen allergens have not yet been addressed in this region.
... Due to this, many taxa, including Sindora got disappeared from the subcontinent but continued flourishing in southeast Asian countries where climate was favouring its growth. The warm phases like PETM and MMCO have also paved the path for the proliferation and diversification of the taxa (Graham, 2011;Adhikari et al., 2022) and it is evident through the diverse fossil records (Spicer et al., 2017;Bhatia et al., 2021). Many plant fossils described from different horizons (Paleocene onwards) indicate the existence of warm and humid climate favouring the luxurious evergreen to semi-evergreen forests on the Indian subcontinent. ...
The plant fossil record of Bhavnagar is poorly documented despite its importance in understanding the evolution of Asian monsoonal ecosystems through time. Three genera of the families Fabaceae and Combretaceae are described from the Gaj Formation of Saurashtra Basin, Gujarat. The sediments of this formation are exposed around Lakhanka-Mithi Virdi villages in the Bhavnagar district of Gujarat and considered of early to middle Miocene in age. This is the first plant fossil record from the region of this age. The described fossil woods i.e. Hopeoxylon speciosum (Navale) Awasthi, Millettioxylon palaeopulchra Lakhanpal et al., and Terminalia tomentosa Wight and Arn. are found similar to the modern genera Sindora Miq., Millettia Wight & Arn (Fabaceae) and Terminalia L. (Combretaceae), respectively. The present distribution of modern comparable forms of the fossil taxa suggests existence of tropical to subtropical forests and warm and humid climatic conditions in the region during the Miocene in contrast to the sub-humid to dry climate seen today.
... However, other clades of ferns diversified during the Cenozoic, and thus they are relatively young. In particular, the order Polypodiales (commonly called polypods), which accounts for c. 80% of current fern species diversity (Hassler, 2004(Hassler, -2021, diversified alongside the angiosperms (Schneider et al., 2004), and many genera of polypods evolved during the past 50 million years (i.e. during the global climate cooling that started in the early Eocene; Graham, 2011). Because phylogenetic relatedness is commonly found to increase with decreasing temperature and precipitation for species in angiosperm assemblages (Qian & Sandel, 2017;Qian et al., 2019), which is consistent with the tropical niche conservatism hypothesis, it appears reasonable to predict that for most species of ferns, phylogenetic diversity decreases and phylogenetic relatedness also increases toward colder and drier environments. ...
Knowledge of relationships between phylogenetic structure of a biological assemblage and ecological factors that drive the variation of phylogenetic structure among regions is crucial for understanding the causes of variation in taxonomic composition and richness among regions, but this knowledge is lacking for the global flora of ferns. Here, we fill this critical knowledge gap.
We divided the globe into 392 geographic units on land, collated species lists of ferns for each geographic unit, and used different phylogenetic metrics (tip‐ vs basal‐weighted) reflecting different evolutionary depths to quantify phylogenetic structure. We then related taxonomic and phylogenetic structure metrics to six climatic variables for ferns as a whole and for two groups of ferns (old clades vs polypods) reflecting different evolutionary histories across the globe and within each continental region.
We found that when old clades and polypods were considered separately, temperature‐related variables explained more variation in these metrics than did precipitation‐related variables in both groups. When analyses were conducted for continental regions separately, this pattern holds in most cases.
Climate extremes have a stronger relationship with phylogenetic structure of ferns than does climate seasonality. Climatic variables explained more variation in phylogenetic structure at deeper evolutionary depths.
... Rocky outcrops in the tropical deciduous forests that are adjacent to the NA deserts, and considered a major source area for expansions into those deserts, harbor familiar members of diverse desert plant and animal groups, including cacti, agaves, euphorbias, rattlesnakes, and lizards (7, SI Appendix, Fig. S1). In these and other forested environments, edaphic outcrops have presented a stable and widespread nucleus for the evolution of drought tolerance; in contrast, widespread dry habitats have been rare throughout time, especially during the cool, moist periods of the Oligocene and early Miocene (3,36,37). ...
Understanding the processes that enable organisms to shift into more arid environments as they emerge is critical for gauging resilience to climate change, yet these forces remain poorly known. In a comprehensive clade-based study, we investigate recent shifts into North American deserts in the rock daisies (tribe Perityleae), a diverse tribe of desert sunflowers (Compositae). We sample rock daisies across two separate contact zones between tropical deciduous forest and desert biomes in western North America and infer a time-calibrated phylogeny based on target capture sequence data. We infer biome shifts using Bayesian inference with paleobiome-informed models and find evidence for seven independent shifts into desert habitats since the onset of aridification in the late Miocene. The earliest shift occurred out of tropical deciduous forests and led to an extensive radiation throughout North American deserts that accounts for the majority of extant desert rock daisies. Estimates of life history and micro-habitat in the rock daisies reveal a correlation between a suffrutescent perennial life history and edaphic endemism onto rocky outcrops, an ecological specialization that evolved prior to establishment and diversification in deserts. That the insular radiation of desert rock daisies stemmed from ancestors preadapted for dry conditions as edaphic endemics in otherwise densely vegetated tropical deciduous forests in northwest Mexico underscores the crucial role of exaptation and dispersal for shifts into arid environments.
... From this perspective, the distinctiveness among environmental niches was likely promoted by climatic oscillations during the Miocene-Pleistocene, which could have contributed to the observed genetic patterns --as suggested by other authors (Graham 2011, Vasconcellos et al. 2020) -promoting the formation of new lineages with particular niches in each case. For example, it has been suggested that during the Last Glacial Maximum, many species survived in refuge areas; in other words, some taxa were able to isolate themselves in non-continuous areas with stable habitats during climatic fluctuations, leading to greater endemism and isolation due to vicariance and selective pressure (Haffer 1969). ...
Boana is a genus of Neotropical treefrogs that includes seven groups of morphologically similar species with a complex and interrelated taxonomic history. Despite recent studies describing the external morphology and phylogenetic history among closely related species, their distributional patterns remain poorly understood. In this study, we used present-day environmental variables (climate, vegetation, elevation, and rivers distance) and historical presence records to describe the geographic distributions of four parapatric closely related species in southeastern South America: Boana curupi, B. stellae, B. semiguttata, and B. joaquini. We then assessed whether the distributions of these species are related to environmental gradients determined by climatic and topographic parameters. To do this, we used niche similarity tests on the principal components derived from environmental variables and on the geographical projection of their niches. Our results showed that 83.3% of the paired comparisons had no or very limited overlap (< 0.20 scores) in ecological space. The niche conservatism hypothesis was accepted between B. stellae – B. curupi and B. stellae – B. semiguttata. Also, we observed a relatively low geographical overlap of suitable environments among species. Analysis of variance showed significant differences among nine environmental variables (related to isothermality, annual temperature range, the mean temperature in both wettest and driest quarters of the year, precipitation seasonality, precipitation of warmest quarter of year, elevation, and vegetation) that define the suitability conditions for these four species. These results support the idea that heterogeneity in the environmental conditions across southeastern South America contributed to the diversification and long-term maintenance of the high species richness in Boana. Our novel results allow a better ecological and biogeographic interpretation of the geographic distribution of these four closely related species, support their recognition as valid species, and provide important data for the development of informed conservation strategies.
... Vegetation reconstructions indicate that circumpolar tundra only began to substantially displace boreal forest between roughly 7 and 3 Mya (Micheels et al. 2007;Salzmann et al. 2008;Graham 2011;Pound et al. 2011). Before this period, the high latitude feedback between vegetation and short wave radiation absorption would have been even less positive than it was in MP. ...
The forest-tundra-short wave net radiation feedback is an important climatic feedback, especially due to its potential role in modulating glacial cycles. Little research has been done on how the strength of this feedback might vary with the background climate state. We propose that the feedback has generally strengthened over the last four million years and that it is weaker under warm Northern Hemispheric conditions when tundra is primarily confined to the high Arctic than under cooler conditions in which the forest-tundra boundary lies south across the interiors of the continental land masses. An intermediate-complexity climate-vegetation model was used to analyze the strength of the feedback for two eras, the mid-Pliocene Warm Period (MP) and the pre-industrial Holocene (PI). We applied a “cold” orbital forcing, favorable to Northern Hemispheric glacial inception. The results show that, in the mid-to-high northern latitudes, orbitally-induced vegetation changes alter top-of-atmosphere short wave net radiation about four times as strongly, and the mid-to-high latitude short wave (SW) vegetation feedback is about twice as strong in PI as compared to MP, primarily due to a more southward position of forest and tundra. This SW feedback operates mostly via surface albedo change. Our modeling results support the hypothesized overall increase in the strength of the forest-tundra-short wave feedback as the climate cools from the mid-Pliocene to late Pleistocene, further suggesting an active role for vegetation dynamics in the onset of major Northern Hemispheric glaciation and the increasing amplitude of glacial-interglacial oscillations over the last few million years.
... The early Cretaceous witnessed major changes in the composition of floras and they continued with out getting extinct though minor extinctions reported in marine realm (Raup & Sepkoski, 1984;Sepkoski, 1996;Heimhofer et al., 2004). The pre-Cretaceous flora was mainly composed of non-flowering plants and gradually bennettitaleans as well as araucarians suddenly decreased in abundance and distribution (Graham, 2011). Subsequently this floral composition was replaced by flowering plants (i.e. the angiosperms), the dominant floral elements of the modern terrestrial plant ecosystems. ...
Earth’s terrestrial ecosystem during the early Cretaceous was marked by the dominance of naked seeded plants and appearance of flowering plants. Tectonic changes and evolutionary processes affected southern floras of the globe during this time. Review of Indian early Cretaceous flora distributed in peri and intra–cratonic basins signify homogenity of composition with regional variations. The flora composed of pteridophytes, pteridospermaleans, pentoxylaleans, bennettitaleans, ginkgoaleans, coniferaleans, taxaleans and taxa of uncertain affinity along with sporadic occurrence of flowering plants represent a unique Indian Early Cretaceous flora. Similitude of basinal floras with marginal differences can be attributed to taphonomic limitations and taxonomic angularity. A perusal of available data brings out an opportunity for novelty in floral composition and variable associations dictated by prevailed environmental conditions. The eastern, western and central regions of India hold distinct litho units encompassing plant mega fossils represented by leaf, wood / axis, seed, fructification and associated marker forms. Remarkable tenacity of certain plant groups, which even found in modern flora and vulnerability of many taxa constitute a blend of extinct and extant. The appearance and extinction of certain taxa can be explained as a cumulative affect of evolutionary and climatic factors. Perpetuation of gondwanic floral elements during the early Cretaceous along with newly evolved floral components testifies evolutionary innovations and changing ecological constraints.
... In the last couple of decades, a series of contributions have significantly improved our knowledge of the diversity and affinities of all major lineages of South American metatherians. It is not the purpose of this work to detail such diversity; instead, the following studies offer a general panorama on these topics (the list is not exhaustive and refers mostly to extinct taxa): "Ameridelphia," Horovitz et al. (2009), Oliveira and Goin (2006, 2011 Goin and Abello (2013), and Barmak et al. (2021). A detail of currently recognized families and orders of North and South American metatherians is given in Table 1. ...
... Geological records from the Eocene/Oligocene boundary show a progression of cooling and drying of the global climate (Zachos et al. 2001, Krause et al. 2010. Ranges of tropical taxa shifted south and many underwent localized extinctions (Prothero 2009, Graham 2011. These conditions provided an evolutionary opportunity for rapid colonization and speciation of oaks, and sections Quercus and Lobatae radiated in parallel sympatry from North America into Central America (Hipp et al. 2018, Cavender-Bares 2019. ...
Red oaks (Quercus sect. Lobatae) are a taxonomic group of hardwood trees which occur in swamp forests, subtropical chaparral, and savannahs from Columbia to Canada. They cover a wide range of ecological niches, and many species are thought to be able to cope with current trends in climate change. Genus Quercus encompasses ca. 500 species, of which ca. 80 make up sect. Lobatae. Species diversity is greatest within the southeastern United States and within the northern and eastern regions of Mexico. This review discusses the weak reproductive barriers between species of red oaks and the effects this has on speciation and niche range. Distribution and diversity have been shaped by drought adaptations common to the species of sect. Lobatae, which enable them to fill various xeric niches across the continent. Drought adaptive traits of this taxonomic group include deciduousness, deep tap roots, ring-porous xylem, regenerative stump sprouting, greater leaf thickness, and smaller stomata. The complex interplay between these anatomical and morphological traits have given red oaks features of drought tolerance and avoidance. Here, we discuss physiological and genetic components of these adaptations to address how many species of sect. Lobatae reside within xeric sites and/or sustain normal metabolic function during drought. Although extensive drought adaptation appears to give sect. Lobatae a resilience to climate change, aging tree stands, oak life history traits, and the current genetic structures places many red oak species at risk. Furthermore, oak decline, a complex interaction between abiotic and biotic agents, has severe effects on red oaks, and is likely to accelerate species decline and fragmentation. We suggest that assisted migration can be used to avoid species fragmentation and increase climate change resilience of sect. Lobatae.
... We conducted a stratified analysis, with dispersal probabilities between pairs of areas specified Rose et al., 2018: Ericales;Kriebel et al., 2019: Salvia) and are based on known geological events affecting geographical distributions in such widely dispersed groups. These time slices allowed for testing the importance of continental vicariance and collision as well as the role of possible Northern Hemisphere land bridges (Tiffney, 1985(Tiffney, , 2000Tiffney & Manchester, 2001;Graham, 2011). The wide time range between 0 and 35 Mya was used to allow the potential for relatively easy dispersal between areas given our relatively sparse sampling towards the tips. ...
Lamiaceae are one of the largest and most economically important families of flowering plants. Despite focused study on relationships within subclades, higher-level relationships have been under-studied. Moreover, the herbaceous habit of much of the family has resulted in a poor fossil record and has hampered estimates of divergence times. Using a new dataset of five plastid loci from 178 members of Lamiaceae representing all subfamilies and nearly all tribes, we clarify major infrafamilial relationships and present a robust set of divergence times. We use this phylogenetic hypothesis as a platform to test previous hypotheses regarding the historical biogeography and evolution of major traits in the family. We confirm the placement of subfamily Nepetoideae, show continued uncertainty in the placement of subfamilies Ajugoideae and Premnoideae and highlight extreme discordance with recent results from nuclear data. Lamiaceae originated during the Late Cretaceous as woody plants with nutlet fruits and four stamens, probably in South-East Asia. Most subfamilies diverged during the Eocene, perhaps facilitated by climatic cooling. Our results provide a valuable set of secondary dates for Lamiaceae and highlight the need for focused study of subfamilies Callicarpoideae and Viticoideae. Our results also provide several hypotheses regarding trait or range-dependent diversification.
... Many major clades of plants originated and initially diversified when the Earth's climate was warm and wet during the Cretaceous and Tertiary. Cold and drought tolerances mostly evolved after the initiation of global cooling in the early Eocene (Condamine et al., 2012;Graham, 2011). ...
Aim
Studies focusing on relatively small spatial scales have shown that alien plants are more likely to invade phylogenetically clustered communities, and that the introduction of alien plants further increases phylogenetic clustering in the recipient communities. However, whether these patterns hold at a continental scale remains untested. Here, we investigate the phylogenetic structure of native and alien regional assemblages of angiosperms across North America.
Location
North America north of Mexico.
Time period
Current.
Major taxon studied
Angiosperms (flowering plants).
Methods
We divided North America into 65 regions across two longitudinal zones, and collated native and naturalized alien species lists of angiosperms for each region. Two phylogenetic metrics, which represent different evolutionary depths, were used to quantify phylogenetic structure of angiosperms as a whole and each major clade in each region, and were related to temperature and precipitation using correlation analyses.
Results
We found that alien angiosperm richness is highest in regions with diverse and phylogenetically dispersed native floras. The introduction of alien species nearly uniformly increases phylogenetic clustering.
Main conclusions
Alien species are generally from the same major clades as native species, consistent with Darwin’s preadaptation hypothesis. The results of this study are consistent across a wide range of phylogenetic extents, but not always with analyses conducted at smaller spatial extents.
... For example, Andean uplift (during Eocene and Miocene) likely influenced the climate in South America by increasing aridity in many regions (Armijo et al., 2015) and modifying the Amazon drainage patterns (Hoorn et al., 2010). In the Middle Miocene, the Cerrado biome went through changes in vegetation composition by expanding C4 plants, associated with the establishment of savanna-like vegetation worldwide (Edwards et al., 2010;Graham, 2011). The marine incursions in Middle-Late Miocene inundated the lowland parts of the Chaco region (Hulka et al., 2006) and are hypothesized to have caused the local extinction of species in these lowlands (Garda & Cannatella, 2007). ...
Aim
Species adapt differently to contrasting environments, such as open habitats with sparse vegetation and forested habitats with dense forest cover. We investigated colonization patterns in the open and forested environments in the diagonal of open formations and surrounding rain forests (i.e. Amazonia and Atlantic Forest) in Brazil, tested whether the diversification rates were affected by the environmental conditions and identified traits that enabled species to persist in those environments.
Location
South America, Brazil.
Taxon
Squamata, Lizards.
Methods
We used phylogenetic information and the current distribution of species in open and forested habitats to estimate ancestral ranges and identify range shifts relative to the current habitats. To evaluate whether these environments influenced species diversification, we tested 12 models using a Hidden Geographic State Speciation and Extinction analysis. Finally, we combined phylogenetic relatedness and species traits in a machine learning framework to identify the traits permitting adaptation in those contrasting environments.
Results
We identified 41 total transitions between open and forested habitats, of which 80% were from the forested habitats to the open habitats. Widely distributed species had higher speciation, turnover, extinction, and extinction fraction rates than species in forested or open habitats, but had also the lower net diversification rate. Mean body temperature, microhabitat, female snout–vent length and diet were identified as putative traits that enabled adaptation to different environments, and phylogenetic relatedness was an important predictor of species occurrence.
Main conclusions
Transitions from forested to open habitats are most common, highlighting the importance of habitat shift in current patterns of biodiversity. The combination of phylogenetic reconstruction of ancestral distributions and the machine learning framework enables us to integrate organismal trait data, environmental data and evolutionary history in a manner that could be applied on a global scale.
... 15 Myr BP) of a far warmer global climate than the present one, which was especially pronounced toward polar areas. Within this expansive forest were numerous gymnosperm genera, such as Cedrus, Picea, Pinus and Tsuga, and angiosperm genera -Acer, Betula, Carya, Corylus, Castanea, Fagus, Magnolia, Quercus, Tilia, Ulmus and Liquidambar (Xiang et al., 2000;Graham, 2011). Increased warming during the Tertiary yielded to the cooler Quaternary, leading to the massive glaciers of the LGM over much of what is now boreal forest throughout the Northern Hemisphere (Fig. 4a). ...
Given the global distribution of human populations and their coincidence with temperate deciduous forests, it is likely that when most people consider the term “forest,” what comes to mind most frequently is the temperate deciduous forest biome. Although not to the level of their tropical counterparts, temperate deciduous forests typically display high plant biodiversity and rates of net primary productivity. They contrast sharply, however, with tropical forests in the distribution of biodiversity and productivity. In tropical forests, greatest plant diversity is associated with the vegetation of greatest productivity—trees. By contrast, the greatest plant diversity—up to 90 percent—in temperate deciduous forests occurs among the plants of least physical stature: the herbaceous species. Given the close association between these forests and their use by human populations, whether for food, fiber, habitat, or recreation, it is not surprising that they have been well studied, particularly in North America, and thus have a rich literature going back many years. However, for the very reason of that intensive use, temperate deciduous forests have proved to be an ecological moving target, as timber harvesting, air pollution, and introduced pests (e.g., insects and parasites) have represented a chronic assault on the structure and function of these ecosystems.
... Dispersal probabilities among areas were specified for five separate time slices: 0-10, 10-35, 25-65, 65-90, 90-113 Ma, with dispersal multipliers modified in each time slice based on adjacency of landmasses at each time. These time slices allowed for testing of the importance of continental vicariance and collision as well as the role of possible Northern Hemisphere land bridges (Tiffney, 1985(Tiffney, , 2000Tiffney and Manchester, 2001;Graham, 2011). Additionally, we conducted biogeographical stochastic mapping (Matzke 8 ;Dupin et al., 2017) in BioGeoBEARS with 100 stochastic maps under both DEC and DECj models to examine the timing, type, and number of biogeographical events, and the number of each class of event (e.g., vicariance, sympatry, subset-sympatry, and jump dispersals) given the DEC or DECj model was summarized using the "count_ana_ clado_events" function in BioGeoBEARS. ...
... According to this pattern, several lineages that are current components of the Cerrado flora seem to have evolved more recently from forest ancestors, in a process involving life form transitions and morphological and ecological adaptations (Simon et al. 2009;Zizka et al. 2020). Studies of paleovegetation and paleoclimate also suggest that forest cover has dominated tropical South America since the early Paleogene, while savannas with geoxyphytes and pyrophytes expanded only from the Miocene (e.g., Beerling and Osborne 2006;Simon et al. 2009;Graham 2011). Similar patterns have been also described for African savannas (Maurin et al. 2014;Pennington and Hughes 2014), and there is evidence that most dry habitats of the world expanded from the Miocene as well (Arakaki et al. 2011). ...
The Sapindales comprise one of the hallmark orders in the Neotropics, being an important component of forested and open formations, especially in Brazil. In recent decades, there have been many efforts made to unravel the Brazilian flora and its distribution; among them is the Brazilian Flora 2020 Project, the main goal of which was to produce updated monographs about Brazilian plant groups. In this work, we present a synthesis of the occurrence and distributions of species and genera of Sapindales in Brazil, noting species endemic to the country, as well as the prevalence of the order in Brazilian phytogeographic domains and vegetations. We have shown that Brazil has 1003 native species in 119 genera of six families of Sapindales, with 388 (43%) species endemic to the country, and the Rutaceae and Sapindaceae families being the richest in species, genera and endemics. Diverse species and life forms are found in virtually all vegetations and phytogeographic domains, but mostly in rainforests of the Amazonian and Atlantic Forest domains. Life forms vary greatly across different families, with a prevalence of lianas in Sapindaceae and of trees in Rutaceae. We discuss our results in light of the current patterns of the families and their assemblage in different vegetation and pytogeographic domains of Brazil.
... Mean annual temperature (MAT), in particular, has shown quantitative correlations with ecologically relevant plant traits , suggesting it may be an important determinant of ecological strategies. Mean annual precipitation (MAP) is important for its relation to drought tolerance (Craine et al., 2013), and changes in global precipitation and temperature have jointly helped to shape the development of modern American plant biomes, such as the emergence of arid grasslands (Graham, 2011). ...
Aim Higher elevation habitats contribute substantially to global biodiversity. Nevertheless, we know comparatively little about how diversity patterns differ among alpine and montane communities across different mountain ranges. Here, we characterized the realized niche space of American seed plants to ask whether or not montane or alpine community compositions define climatically distinct species pools at this regional scale. Location Americas. Time Period Contemporary. Major taxa studied Seed plants. Methods We assembled a niche model dataset of 72,372 American seed plants based on digitized and georeferenced specimen records. We used this dataset to quantify occupied abiotic niche space with regards to temperature, precipitation, and elevation. This approach further permitted differentiation of higher-elevation specialists (i.e., ranges centered at high elevations) from generalists (i.e., ranges centered at lower elevations but extending into mountain areas). Results Montane communities did not differ from the regional species pool in terms of richness patterns, occupied climatic niche space, or niche breadth. In contrast, alpine communities were characterized by a bimodal latitudinal diversity gradient, drastically reduced climatic niche space, and broader temperature but narrower precipitation niche breadth. Alpine generalists further showed statistically significant differences in temperature, but not precipitation, niche breadth from both alpine specialists and lowland taxa. We also highlight non-alpine species whose climatic niche space otherwise overlapped with that of alpine plants. These species were geographically concentrated in the southern US and Mexico, tended to have a greater fraction of their ranges in frost-exposed mountain foothills, and less of their range in lowland, frost-free, areas, compared to other non-alpine species. Main conclusions These results suggest that ecological and physiological barriers, rather than dispersal limitation might better explain alpine community assembly and that alpine, but not montane, communities form a climatically distinct species pool in the Americas.
... This orogeny was partially contemporary to the accretion of the Western Cordillera, a process that initiated during the Oligocene and early Miocene, and caused the creation of high-altitude habitats, above ca. 4000 m, during the late Miocene (Kroonenberg et al., 1990;Graham, 2011). These uplifts are presumed to have had a significant impact on biogeographic patterns, especially as a physical barrier to dispersal of lowland restricted organisms (Pirie et al., 2006;Pennington et al., 2010;Richardson et al., 2018). ...
Understanding how species diversify and evolve in species-rich areas like the lowland rain forest in the Neotropics is critical for conservation in times of unprecedented threats. To determine how the Andean uplift, the formation of the Panama land bridge, and Pleistocene climatic fluctuations affected dispersal and diversification in the Sapotaceae subfamily Chrysophylloideae, we collected 146 Chrysophylloideae accessions in previously under-explored areas, generating one of the most geographically complete data sets for neotropical Sapotaceae. Sapotaceae is a good model to test diversification hypotheses in lowland neotropical rain forests as it predominantly occurs <1000 m altitude, and it is an abundant and species-rich group in this biome. We generated a time calibrated phylogeny of 123 Sapotaceae species based upon the nuclear ribosomal internal transcribed spacer region that suggests migration between lineages to the east and the west Andean Cordilleras occurred before and after periods of major uplift, indicating that the Andes did not represent a significant barrier to dispersal for Sapotaceae, although it may have promoted vicariance in some cases. Dispersal between South and Central America occurred mainly prior to the formation of the Panama land bridge, suggesting that this event did not affect migration patterns in Chrysophylloideae. We inferred diversification rates and detected three shifts in the phylogeny, but they are not congruent with tectonic movements during the middle Miocene and climatic changes during the Pleistocene. Finally, some species with restricted distributions appear to be phylogenetically nested within species with broader ranges, suggesting ancestor descendent relationships and insights into patterns of speciation in rain forest trees.
... This was a period of climatic instability, when tundra-like ecosystems expanded across polar and alpine regions as the Earth's climate became progressively cooler and drier towards the onset of the late Pliocene glaciations, ca. 3 Ma. (Mosbrugger et al., 2005;Graham, 2010Graham, , 2011. The Miocene-Pliocene boundary was also identified as a period of diversification in other parmelioid lineages (Amo de Paz et al., 2011;Leavitt et al., 2012bLeavitt et al., , 2012cLeavitt et al., , 2015b, driven directly by major geological events, and indirectly by associated changes in climatic conditions (Zachos et al., 2001). ...
Widespread geographic distributions in lichens have been usually explained by the high dispersal capacity of their tiny diaspores. However, recent phylogenetic surveys have challenged this assumption and provided compelling evidence for cryptic speciation and more restricted distribution ranges in diverse lineages of lichen-forming fungi. To evaluate these scenarios, we focus on the fungal genus Pseudephebe (Parmeliaceae) which includes amphitropical species, a distribution pattern whose origin has been a matter of debate since first recognized in the nineteenth century. In our study, a six-locus dataset and a broad specimen sampling covering almost all Earth’s continents is used to investigate species delimitation in Pseudephebe. Population structure, gene flow and dating analyses, as well as genealogical reconstruction methods, are employed to disentangle the most plausible transcontinental migration routes, and estimate the timing of the origin of the amphitropical distribution and the Antarctic populations. Our results demonstrate the existence of three partly admixed phylogenetic species that diverged between the Miocene and Pliocene, and whose Quaternary distribution has been strongly driven by glacial cycles. Pseudephebe minuscula is the only species showing an amphitropical distribution, with populations in Antarctica, whereas the restricted distribution of P. pubescens and an undescribed Alaskan species might reflect the survival of these species in European and North American refugia. Our microevolutionary analyses suggest a Northern Hemisphere origin for P. minuscula, which could have dispersed into the Southern Hemisphere directly and/or through “mountain-hopping” during the Pleistocene. The Antarctic populations of this species are sorted into two genetic clusters: populations of the Antarctic Peninsula were grouped together with South American ones, and the Antarctic Continental populations formed a second cluster with Bolivian and Svalbard populations. Therefore, our data strongly suggest that the current distribution of P. minuscula in Antarctica is the outcome of multiple, recent colonizations. In conclusion, our results stress the need for integrating species delimitation and population analyses to properly approach historical biogeography in lichen-forming fungi.
... The sudden appearance of angiosperms during the Early Cretaceous and their further dominance in the later part of the Cretaceous is a Darwin's abominable mystery (Friedman, 2009). The origin and rapid explosion of this plant group changed the face of Earth and provides the structural definition for most terrestrial ecosystems (Crepet, 2000;Graham, 2011). The diversification of this group also assisted in the coevolution of various new organisms in the animal kingdom such as insects (Grimaldi and Engel, 2005). ...
This study presents the first report of angiosperm macrofossil assemblage from the Early Cretaceous sediments of India, containing a fruit, a spike, a petal, leaves, and an axis from the Krishna Godavari Basin. This assemblage provides clues to angiosperm evolution and ecology during the Early Cretaceous of India. The described enigmatic forms are comparable to fruits of Trapa, and palm leaves and spikes of Potamogeton. The fossil material also includes ribbon-like leaves with a small axis; fossil remains suggest affinity with the monocotyledon group and support recent morphological and molecular phylogenetic studies to establish the divergence of this group from dicotyledons, during the early Cretaceous. Fossils described in the present study suggest an affinity for an aquatic environment that appears to be ideal for some early angiosperms.
Niche convergence or conservatism have been proposed as essential mechanisms underlying elevational plant community assembly in tropical mountain ecosystems. Subtropical mountains, compared to tropical mountains, are likely to be shaped by a mixing of different geographic affinities of species and remain somehow unclear. Here, we used 31 0.1-ha permanent plots distributed in subtropical forests on the eastern and western aspects of
the Gaoligong Mountains, southwest China between 1498 m and 3204 m a.sl. to evaluate how niche-based and biogeographic processes shape tree community assembly along elevational gradients. We analyzed the elevational patterns of taxonomic, phylogenetic and functional diversity, as well as of individual traits, and assessed the relative importance of environmental effects on these diversity measures. We then classified tree species as
being either tropical affiliated or temperate affiliated and estimated their contribution to the composition of biogeographic affinities. Species richness decreased with elevation, and species composition showed apparent turnover across the aspects and elevations. Most traits exhibited convergent patterns across the entire elevational
gradient. Phylogenetic and functional diversity showed opposing patterns, with phylogenetic diversity increasing and functional diversity decreasing with elevation. Soil nutrients, especially phosphorus and nitrogen, appeared to be the main abiotic variables driving the elevational diversity patterns. Communities at lower elevations were occupied by tropical genera, while highlands contained species of tropical and temperate biogeographic affinities.
Moreover, the high phylogenetic diversity at high elevations were likely due to differences in evolutionary history between temperate and tropical species. Our results highlight the importance of niche convergence of tropical species and the legacy of biogeographic history on the composition and structure of subtropical mountain forests. Furthermore, limited soil phosphorus caused traits divergence and the partitioning for different forms of phosphorus may explain the high biodiversity found in phosphorus-limited subtropical forests.
This review explores the evolution of extant South American tropical biomes, focusing on when and why they developed. Tropical vegetation experienced a radical transformation from being dominated by non‐angiosperms at the onset of the Cretaceous to full angiosperm dominance nowadays. Cretaceous tropical biomes do not have extant equivalents; lowland forests, dominated mainly by gymnosperms and ferns, lacked a closed canopy. This condition was radically transformed following the massive extinction event at the Cretaceous–Paleogene boundary. The extant lowland tropical rainforests first developed at the onset of the Cenozoic with a multistratified forest, an angiosperm‐dominated closed canopy, and the dominance of the main families of the tropics including legumes. Cenozoic rainforest diversity has increased during global warming and decreased during global cooling. Tropical dry forests emerged at least by the late Eocene, whereas other Neotropical biomes including tropical savannas, montane forests, páramo/puna, and xerophytic forest are much younger, greatly expanding during the late Neogene, probably at the onset of the Quaternary, at the expense of the rainforest.
There is disparity between the estimated time of origin
of the ‘superclade’ Dipterocarpaceae sensu lato, that
includes Sarcolaenaceae, Cistaceae, Pakaraimaea, Bixaceae,
Cochlospermaceae and Sphaerosepalaceae, as determined by
recent molecular phylogenies (100−85 million years ago, Ma) and
its strongly tropical, South American-African-Madagascan-SE Asian
distribution that indicates an older Gondwanan origin (>110 Ma).
We used several paleobiogeographic approaches, including
recently reported fossil records, to explore the hypothesis that
Dipterocarpaceae sl has a Gondwanan/early-Cretaceous origin.
We created molecular phylogenies for this group, assigned
each genus/family to the tectonic plate on which it is extant, and
subjected the cladogram to areogram analysis. We also assessed
ecological, mycotrophic and morphological traits, and global
circulation patterns, as these might affect this group’s distribution.
The initial analysis (omitting fossil evidence) showed that the
crown of Dipterocarpaceae sl occurred concurrently on the South
American and Madagascan plates. Including fossils from Africa and
India changed this to a South American-African origin. Collectively,
these origins represent NorthWest Gondwana with South America,
Africa and Madagascar remaining conjoined until ≥105–115 Ma,
setting the minimum age for this superclade with some evidence
that it may be much older. We also show that the immediate
ancestors of the three daughter lineages [Dipterocarpaceae-
Sarcolaenaceae (in Africa/Madagascar, ≥115 Ma), Cistaceae-
Pakaraimaea (South America/Africa/Eurasia, ≥105 Ma) and
Bixaceae-Cochlospermum-Sphaerosepalaceae (South America/
Africa, ≥105 Ma)] also arose in NorthWest Gondwana.
The immediate ancestors or basal species in Sarcolaenaceae,
Sphaerosepalaceae, Dipterocarpaceae (both its subfamilies) and
Bixaceae migrated from (South America)/Africa to Madagascar
and we propose that the Dipterocarpoideae proceeded from
Africa to India while still linked to Madagascar. In addition, much
subsequent diversification of this superclade has occurred on the
Eurasian, Indian, SE Asian (Sunda) and North American plates
post-Gondwanan breakup.
This long vicariant history is supported by fossil, ecological,
mycotrophic and morphological traits, and global circulation
patterns that show negligible propensity for transoceanic dispersal
to explain this clade’s wide intercontinental distribution.
We conclude that all these areocladogram/plate-breakup/
ecomorphological/circulation features are consistent with
a Gondwanan/early-Cretaceous (>115 Ma) origin for the
Dipterocarpaceae-Cistaceae-Bixaceae superclade plus its three
daughter clades. Future analyses at the species level, exploring
alternative diversification dates from both fossils and platetectonic
dynamics, are needed to refine these findings.
Understanding the processes that enable organisms to shift into more arid environments as they emerge is critical for gauging resilience to climate change, yet these forces remain poorly known. In a comprehensive clade-based study, we investigate recent shifts into North American deserts in the rock daisies (Perityleae), a diverse tribe of desert sunflowers (Compositae). We sample Perityleae across two separate contact zones between tropical deciduous forest and desert biomes in western North America and infer a time-calibrated phylogeny based on target capture sequence data. We reconstruct biome shifts using Bayesian inference with paleobiome-informed models and find evidence for seven independent shifts into desert habitats since the onset of aridification in the late Miocene epoch. The earliest shift occurred out of tropical deciduous forests and led to an extensive radiation throughout North American deserts that accounts for the majority of extant desert Perityleae. Reconstructions of life history and micro-habitat in Perityleae reveal a correlation between a suffrutescent perennial life history and edaphic endemism onto rocky outcrops, an ecological specialization that evolved prior to establishment and diversification in deserts. That the insular radiation of desert rock daisies stemmed from ancestors pre-adapted for dry conditions as edaphic endemics in otherwise densely vegetated tropical deciduous forests in northwest Mexico underscores the crucial role of exaptation and dispersal for shifts into arid environments.
Significance Statement
The environmentally stressful conditions found in desert regions have often been implicated as the main factor in the evolution of drought tolerance in desert plants. Yet many iconic desert plant lineages evolved prior to the recent emergence of widespread arid climates, suggesting an important role for pre-adaptation (exaptation). In the desert rock daisies (Perityleae), we provide empirical support for this view by showing that life history evolution associated with their ecological specialization onto rock outcrops was a precursor to their establishment and extensive diversification in North American deserts. We caution against assuming the presence of ancient dry biomes based on time-calibrated phylogenies and we emphasize the fundamental roles that exaptation and dispersal play during community assembly in novel environments.
Phylogenetic diversity analyses were used to interpret the timing and assembly of vegetation communities in temperate New Zealand. A data set comprising 1638 permanent vegetation plots provided plant-distributional data, and a plastid rbcL phylogenetic tree provided phylogenetic metrics. Mean crown age, standardized effect size of mean pairwise distance and standardized effect size of mean nearest taxon distance were analysed in relation to taxonomic groups (angiosperms, gymnosperms and pteridophytes), life form (woody angiosperms, non-woody angiosperms) and temperature and precipitation using generalized additive models. Angiosperms in South Island have a younger crown age than those in most North Island sites, and phylogenetic clustering is prevalent throughout. Angiosperms and pteridophytes from drier and cooler open-habitat communities in central and eastern South Island have younger crown ages and phylogenetic clustering compared to wetter and warmer closed-habitat communities of western South Island and North Island, with older crown ages and phylogenetic over-dispersion. Phylogenetic clustering is consistent with species-rich radiations that have diversified into newly available niches during the late Miocene to Plio-Pleistocene. Pteridophytes displayed less phylogenetic relatedness than angiosperms, reflecting their older crown ages. These findings are consistent with a view that northern New Zealand retained older lineages of subtropical origin during glaciations, whereas novel habitats in cool, dry climates in southern New Zealand facilitated more recent radiations. These results emphasize the strong legacy of history in the modern-day composition of plant communities.
Recently published time-calibrated molecular phylogenies have brought to light a large-scale biotic interchange between the Western and Eastern Amazon basins, associated with the late Neogene (c. 10–4.5 Ma) uplift of the Northern Andes and formation of the modern transcontinental Amazon river. This important macroevolutionary event was previously overlooked due to poor understanding of alpha taxonomy and geographic distributions, lack of species-dense phylogenetic analyses, and insufficient methods for estimating biogeographic range evolution and lineage divergence times. Rapid improvements in all these areas have now provided the community with a corpus of historical biogeographic studies using species-dense and time-calibrated molecular phylogenies of plant and animal taxa distributed across Greater Amazonia. In this study we present historical biogeographic analyses of two clades of freshwater fishes (potamotrygonid stingrays and apteronotid electric fishes), and synthesize these results with those of 18 other published studies of Amazonian taxa, including riverine and upland (terra firme) clades of plants (n = 5), insects (n = 2), and representatives of all five vertebrate classes; i.e. fishes (n = 4) amphibians (n = 3), non-avian reptiles (n = 2), birds (n = 2), and mammals (n = 2). Our results support the hypothesis that tectonically-driven megariver capture events facilitated a massive biotic interchange between the Western and Eastern Amazon basins, which we name the Great Amazonian Biotic Interchange. These same megacapture events also separated the modern Amazon and Orinoco basins, contributing to the biotic distinctiveness of these megadiverse regions, and thereby elevating the total biodiversity of Greater Amazonia. The results highlight the role of large and rare (Black Swan) landscape evolution events in preserving and promoting biodiversity that had accumulated over tens of millions of years and across the whole of the South American continental platform.
Late Cretaceous plants from the North Sudetic Basin (Lower Silesia, south-western Poland) are reviewed on the basis of megaflora from 17 localities (270 identifiable specimens), mesoflora from two localities, and microflora from four localities. Major sites are Rakowice Małe and Bolesławiec. Eight megafloral assemblages are distinguished (Assemblage 1, Turonian; Assemblages 2, 3, lower–middle Coniacian; Assemblages 4, 5, upper Coniacian?–lower Santonian?; Assemblages 6–8, lower–middle Santonian); the bulk of the palaeoflora is from Assemblages 4–6 and 8. Megaflora consists of 29 taxa (6 ferns, 4 conifers, and 19 angiosperms). Geinitzia reichenbachii is the most common species. Dryophyllum westerhausianum (Richter, 1904) Halamski and Kvaček comb. nov. is a trifoliolate leaf re-interpreted as a representative of Fagales. Three species of Dewalquea are distinguished: Dewalquea haldemiana, Dewalquea insignis, and Dewalquea aff. gelindenensis. Platanites willigeri Halamski and Kvaček sp. nov. is characterised by trifoliolate leaves, the median leaflet of which is ovate, unlobed, with a serrate margin, and cuneate base. Palaeocommunities inferred from the megafossil record include: a back swamp forest dominated by Geinitzia, with abundant ferns; a Dryophyllum-dominated riparian forest; a forest with Dewalquea and Platanites willigeri possibly located in the marginal part of the alluvial plain; dunes with D. haldemiana and
Konijnenburgia; a fern savanna with patches of Pinus woodlands. Palynoassemblage A from the Nowogrodziec Member, studied mostly at Rakowice Małe and Żeliszów, consists of 126 taxa, including 105 terrestrial palynomorphs (54 bryophyte, lycophyte, and pteridophyte spores, 16 gymnosperms, 35 angiosperms). The mega- and mesofossil records are dominated by angiosperms; the palynoassemblages are dominated by ferns. Palaeocommunities represented solely by the microfossil record are halophytic (with Frenelopsis and unconfirmed presence of Nypa) and pioneer vegetation. Palaeocommunities
are intermediate in general character between those pre-dating the Cretaceous Terrestrial Revolution and modern, angiosperm-
dominated vegetation. In comparison to older plant assemblages from contiguous areas laurophylls are much rarer;
this might correspond to a real phenomenon of exclusion of lauroids from Santonian riparian forests. The studied assemblage
is more similar to younger palaeofloras than to older ones; this might be interpreted as stabilisation of communities
after a period of pronounced change related to the rise to dominance of the angiosperms. In contrast to widespread endemism
among vertebrates of the European Archipelago, the plant cover consists mostly of species that are widely distributed.
The implementation of explicit phylogenetic techniques to the study of relationships among angiosperms has led to the recognition of a major monophyletic group, the eudicot clade, characterized by the production of tricolpate or tricolpate-derived pollen grains. Eudicots comprise nearly 75% of extant angiosperm species (subclasses Hamamelididae, Caryophyllidae. Dilleniidae, Rosidae, and Asteridae, as well as the order Ranunculales in the Magnoliidae sensu Cronquist). Recent phylogenetic analyses, based on both morphological data and molecular sequences, have begun to clarify higher-level phylogenetic relationships within the eudicot clade. The basalmost branch within the eudicots separates a small ranunculid clade, which includes the Ranunculales and Papaverales. The main group within the eudicots, here referred to as the main cudicot clade, is formed by a basal grade of species-poor lineages, mostly of "lower" Hamamelididae, and a large monophyletic group, here referred to as core eudicots, which includes ca. 97% of eudicot species diversity. Within the core eudicots, three distinct groups can be recognized. (1) The caryophyllid clade (ca. 6% of eudicot species diversity) includes the Caryophyllidae as traditionally defined and a few additional taxa previously thought to be of dilleniid and rosid affinity. (2) The rosid clade (ca. 39% of total eudicot species diversity) is composed mostly of taxa previously included in Dilleniidae and Rosidae, and includes a well-supported clade that we term here the core rosids (ca. 24% of total eudicot species diversity). Among the taxa in the core rosid clade are the Fabaceae, Rosaceae, Linales, and Cunoniaceae, as well as some families of Violales, and the "higher" Hamamelididae. (3) The asterid clade (ca. 50% of eudicot species diversity) consists of two large clades composed mostly of taxa previously assigned to Asteridae, and additional members of Rosidae and Dilleniidae. One of these large asterid clades is dominated by the Asterales s.l. (ca. 17% of total eudicot species diversity), while the other corresponds to a broadly defined Lamiidae (ca. 26% of total eudicot species diversity). Paleobotanical data first document the presence of early cudicots ca. 125 million years before the present (Barremian-Aptian boundary, Lower Cretaceous), prior to the major diversification and ecological radiation of angiosperms. Well-preserved floral remains and other fossils provide a minimum age for the origin of eudicot lineages. Sediments of Albian age contain floral remains of Platanaceae and probable Buxaceae, both of which fall within the species-poor lineages at the base of the main eudicot clade. In slightly younger sediments, the taxonomic diversity of eudicots increases considerably. Basal taxa in the core eudicots are represented by Hamamelidaceae and by several flowers of broad saxifragalean affinity in Turonian-Campanian strata. Among taxa within the rosid clade, the Capparales and Myrtales are documented from the Turonian and Santonian-Campanian, respectively. The core rosids are represented by several flowers with affinities to Juglandales, Myricales, and Fagales in the Santonian-Campanian. Flowers with possible affinities to Hydrangeaceae, from the Coniacian-Santonian, represent the basalmost group within the asterid clade, and flowers of broad ericalean affinity (including Actinidiaceae), from the Turonian-Campanian, document the presence of several groups within the ericalean clade. The Asteridae s.l. are not securely represented in the Upper Cretaceous, and, to our knowledge, there is no reliable Cretaceous record for any member of the Lamiidae s.l. Although nearly all of the main eudicot clades are represented by at least one of their included lineages in the Upper Cretaceous, the earliest well-documented records of the Fabaceae, Asteraceae, Lamiales s.l., and Gentianales, which together comprise ca. 45% of total eudicot species diversity, are found in uppermost Cretaceous (Maastrichtian) or Tertiary sediments. The three subfamilies of Fabaceae are well documented by flowers and fruits in the Eocene, although the presence of pollen grains assigned to Caesalpinioideae from Maastrichtian strata suggests that the family extends back into the uppermost Cretaceous. The Asteraceae, Lamiales s.l., and Gentianales are known from the Paleogene based mostly on vegetative remains. The uneven distribution of species diversity among the major clades of eudicots, and the fact that the most species-rich groups are known only from relatively young fossils, suggests that a significant portion of eudicot diversity is the result of relatively recent radiations that occurred during the second half of angiosperm evolutionary history. The evolutionary basis for the explosive diversification of specific eudicot clades-in terms of exceptionally high speciation rates, low extinction rates, or both-remains uncertain.
The evolution of grasses using C₄ photosynthesis and their sudden rise to ecological dominance 3 to 8 million years ago is among the most dramatic examples of biome assembly in the geological record. A growing body of work suggests that the patterns and drivers of C₄ grassland expansion were considerably more complex than originally assumed. Previous research has benefited substantially from dialog between geologists and ecologists, but current research must now integrate fully with phylogenetics. A synthesis of grass evolutionary biology with grassland ecosystem science will further our knowledge of the evolution of traits that promote dominance in grassland systems and will provide a new context in which to evaluate the relative importance of C₄ photosynthesis in transforming ecosystems across large regions of Earth.
In northern South America the Cenozoic was a period of intense tectonic and climatic interaction that resulted in a dynamic Amazonian landscape dominated by lowlands with local and shield-derived rivers. These drainage systems constantly changed shape and size. During the entire Cenozoic, the Brazilian and Guiana Shields were stable mountainous areas. Andean-derived river systems increased in importance especially in the Neogene. A remarkable feature in western Amazonian history is the waxing and waning of large lake systems and embayments. By the Late Miocene (about 11 Ma), the Andes were connected with the Atlantic through an incipient Amazon River, and from c. 7 Ma Andean-derived river systems became fully established in central and eastern Amazonia and the modern landscape configuration had developed. Rainforests already existed in northern South America during the Paleogene, but the modern rainforests – with resemblance to the Present forest – only developed during the Miocene. The western Amazonian Miocene record contains very diverse aquatic faunas (molluscs, ostracods, turtles, crocodiles, fishes) as well as terrestrial mammals. Remarkable gigantic forms thrived in Amazonian ecosystems at the time. Since the Late Miocene, edaphically heterogeneous lands emerged in western Amazonia in areas previously occupied by lake systems. At the same time nutrient-rich deposits spread over central and eastern Amazonia, an event that, based on molecular phylogenetic studies on extant taxa, coincided with diversification of terrestrial taxa. Molecular-based time estimates confirm the steady diversification and mostly pre-Quaternary origin of extant Amazonian taxa. A significant portion of the current species richness is attributed to a combination of relatively constant wet and warm climates and a heterogeneous edaphic substrate. The Quaternary was a time of distribution shifts, but can no longer be considered a time of diversification in Amazonia.
Few South American macrofloras of Paleocene age are known, and this
limits our knowledge of diversity and composition between the
end-Cretaceous event and the Eocene appearance of high floral diversity.
We report new, unbiased collections of 2516 compression specimens from
the Paleocene Salamanca Formation (ca. 61.7 Ma) from two localities in
the Palacio de los Loros exposures in southern Chubut, Patagonia,
Argentina. Our samples reveal considerably greater richness than was
previously known from the Paleocene of Patagonia, including 36 species
of angiosperm leaves as well as angiosperm fruits, flowers, and seeds;
ferns; and conifer leaves, cones, and seeds. The floras, which are from
siltstone and sandstone channel-fills deposited on low-relief floodplain
landscapes in a humid, warm temperate climate, are climatically and
paleoenvironmentally comparable to many quantitatively collected
Paleocene floras from the Western Interior of North America. Adjusted
for sample size, there are >50% more species at each Palacio de los
Loros quarry than in any comparable U.S. Paleocene sample. These results
indicate more vibrant terrestrial ecosystems in Patagonian than in North
American floodplain environments ˜4 m.y. after the end-Cretaceous
extinction, and they push back the time line 10 m.y. for the evolution
of high floral diversity in South America. The cause of the dis parity
is unknown but could involve reduced impact effects because of greater
distance from the Chicxulub site, higher latest Cretaceous diversity, or
faster recovery or immigration rates.
Two aquatic plant genera assignable to Decodon (Lythraceae) and Ceratophyllum (Ceratophyllaceae) are described based on reproductive structures collected from the Cerro del Pueblo Formation (late Campanian [73.5ma]), Coahuila, Northeast Mexico. Decodon is represented by three small seeds with a pyramidal shape, rounded borders, and a concave ventral surface with a rectangular valve towards the center of the seed ventral surface. The Ceratophyllum spiny fruit has an ellipsoidal central body and two proximal long spines flanking a short pedicel opposite the stylar projection. These new reports confirm the presence of both genera in the Upper Cretaceous sediments of Northeastern Mexico, and add to our recognition of diversity within the widely distributed freshwater communities along the margin of the epicontinental sea.
A fossil flora from the Late Paleocene-Early Eocene Thyra O Formation of eastern North Greenland (paleolatitude 77-degrees N) has yielded monocotyledon leaf impressions with characters seen only in the closely related modem species in the families of Heliconiaceae, Musaceae, and Strelitziaceae. The combination of large costae widths and parallel, nonanastomosing, lateral veins that depart at right angles from the costae in the fossil material are features present only in leaves of extant species from these families. Three basic venation patterns also are recognized in the modem species of these families, but except for the genera Strelitzia and Phenakospermum, none of these patterns are present exclusively in any one family. Musopsis n. gen. is created for. the fossil material from Greenland, but it is considered a form genus due to the lack of gross morphological features that can be used for separating leaves of the modem genera in Heliconiaceae, Musaceae, and Strelitiziaceae. It is the first known Arctic occurrence of fossil leaf material resembling this modern group of taxa.
The Physical Geography of South America, the eighth volume in the Oxford Regional Environments series, presents an enduring statement on the physical and biogeographic conditions of this remarkable continent and their relationships to human activity. It fills a void in recent environmental literature by assembling a team of specialists from within and beyond South America in order to provide an integrated, cross-disciplinary body of knowledge about this mostly tropical continent, together with its high mountains and temperate southern cone. The authors systematically cover the main components of the South American environment - tectonism, climate, glaciation, natural landscape changes, rivers, vegetation, animals, and soils. The book then presents more specific treatments of regions with special attributes from the tropical forests of the Amazon basin to the Atacama Desert and Patagonian steppe, and from the Atlantic, Caribbean, and Pacific coasts to the high Andes. Additionally, the continents environments are given a human face by evaluating the roles played by people over time, from pre-European and European colonial impacts to the effects of modern agriculture and urbanization, and from interactions with El Niño events to prognoses for the future environments of the continent.
A fossil herbaceous angiosperm, Pluricarpellatia peltata gen. et sp. nov., is described from the Lower Cretaceous Crato Formation of northeastern Brazil. The description is based on several nearly complete specimens with roots, cordate, excentrically peltate to centrally peltate leaves, and flowering structures with in situ seeds. The seeds are smooth to verrucate and have the micropyle and hilum close together and have laminar placentation. Pluricarpellatia shares several characters with extant Nymphaeales, such as a rhizomatous growth form and simple, petiolate, peltate leaves, and laminar placentation. Similarities to Cabombaceae include an apocarpous gynoecium. However, the carpel morphology clearly differs from extant Cabombaceae so that Pluricarpellatia is considered to represent an extinct member of Nymphaeales, most likely branching off early in this lineage, and may thus be the most basal member of this clade described so far. In addition to Pluricarpellatia an unnamed nymphaealean plant (Taxon A), possibly belonging to the Nymphaeaceae, is described. During the late Aptian to earliest Albian representatives of Nymphaeales may have already developed a moderate diversity.
Tertiary benthic and planktonic foraminiferal oxygen isotope records are
correlated to a standard geomagnetic polarity time scale, making use of
improved chronostratigraphic control and additional Oligocene isotope
data. Synchronous changes in both benthic and planktonic
δ18O values which occurred in the Oligocene to Miocene
(36-5.2 Ma) are interpreted, in part, to represent ice growth and decay.
The inferred ice growth events correlate with erosion on passive
continental margins as interpreted from seismic and chronostratigraphic
records. This association is consistent with a link between Oligocene to
Miocene erosional events and rapid (>15 m/m.y.) glacioeustatic
lowerings of about 50 m. High benthic foraminiferal
δ18O values suggest the presence of continental ice
sheets during much of the Oligocene to Recent (36-0 Ma). Substantially
ice-free conditions probably existed throughout the Paleocene and Eocene
(66-36 Ma). The mechanisms and rates of sea level change apparently were
different between the early and late Tertiary, with glacioeustatic
changes restricted to the past 36 m.y. Pre-Oligocene erosion on passive
continental margins was caused by eustatic lowerings resulting from
global spreading rate changes. We apply a model which suggests that
large areas of the continental shelves were subaerially exposed during
such tectonoeustatic lowstands, stimulating slope failure and submarine
erosion. The different mechanisms and rates of eustatic change may have
caused contrasting erosional patterns between the early and late
Tertiary on passive continental margins. This speculation needs to be
confirmed by examination of data from several passive margins.
Nearly all of the species diversity in Piperaceae is encompassed within Piper and Peperomia. Both genera are pan-tropical with areas of diversification in the Neotropics and Southeast Asia. Piperaceae are less diverse
in Africa with only two native species of Piper. This study examines the distribution of both Piper and Peperomia with representative samples from the Neotropics, Asia, Pacific Islands, and Africa. Molecular dating is used to place an
age for the crown clades of Piper and Peperomia as well as ages for diversification within the clades. Both genera have origins in the late Cretaceous, but species level
diversification occurred much later in the Tertiary. Biogeography of both genera are correlated with paleoclimate evidence
to better explain the distribution and diversification of these large genera.
The arrival of hipparionine horses in the eastern Mediterranean region around 11 Ma was traditionally thought to mark the simultaneous westward expansion of savanna vegetation across Eurasia. However, recent paleoecological reconstructions based on tooth wear, carbon isotopes, and functional morphology indicate that grasses played a minor role in Late Miocene ecosystems of the eastern Mediterranean, which were more likely dry woodlands or forests. The scarcity of grass macrofossils and pollen in Miocene floras of Europe and Asia Minor has been used to support this interpretation. Based on the combined evidence, it has therefore been suggested that Late Miocene ungulate faunal change in the eastern Mediterranean signals increased aridity and landscape openness, but not necessarily the development of grass-dominated habitats.
In the online-only Methods of our Letter, equation (3) was published incorrectly. It should read: (Formula presented) Also, some data in Supplementary Table 2 was incorrectly ordered (J. A. Rivas and P. T. Andreadis brought this to our attention). Supplementary Table 2 and equation (3) have been corrected online.
An assemblage of 33 fossil pollen and spores, recovered from the 3600-m high Pislepampa locality of E. W. Berry, Eastern Cordillera, Bolivia, adds considerably to our knowledge of three aspects of the region in late Neogene time: (1) the paleovegetation, (2) the paleoclimate, and (3) the paleoelevation of the Central Andes. The plant microfossils recognized are Isoetes, Lycopodium (three types), Cnemidaria, Cyathea (three types), Grammitis, Hymenophyllum, Pteris, trilete fern spores (two types), Danaea, monolete fern spores (four types), Podocarpus, Gramineae, Palmae, Ilex, cf. Oreopanax, Cavanillesia, cf. Pereskia, Compositae (three types), Ericaceae, Tetrorchidium, and unknowns (three types). The diversity of the Compositae suggest that this flora has a maximum age around the Miocene-Pliocene boundary, that is, 6-7 million years. All members of the paleocommunity presently grow in the bosque montano húmedo (cloud forest) along the eastern slope of the Central Andes of Bolivia, which occurs between MATs (mean annual temperatures) of ∼10° and 20°C. The Pislepampa flora probably represents the lower limits of this forest because the fossil leaves collected by Berry from the same locality all have entire margins, suggesting that the flora grew near the cloud forest-tropical forest transition. Presently, the lower limit of the cloud forest forest has MATs of ∼20°C, a mean annual precipitation between 1000 and 1500 mm, and that part containing most of the identified genera of fossil pollen is found at elevations ∼1200-1400 m. These conditions are thus inferred for the Pislepampa flora; however, because of the uncertainty of the magnitude of global climate change and of possible changes in the ecological range of plant genera, we estimate an error of at least ±1000 m for the paleoelevation estimate. When the total uplift is corrected for probable amounts of erosionally driven isostatic rebound, the paleoelevation estimate suggests that from one-third to one-half of the uplift of the Eastern Cordillera had occurred by the beginning of the Pliocene. This estimate is consistent with other paleoelevation estimates from the Central Andes.
Molecular estimates of the age of angiosperms have varied widely, and many greatly predate the Early Cretaceous appearance of angiosperms in the fossil record, but there have been few attempts to assess confidence limits on ages. Experiments with rbcL and 18S data using maximum likelihood suggest that previous angiosperm age estimates were too old because they assumed equal rates across sites-use of a gamma distribution of rates to correct for site-to-site variation gives 10-30 my (million years) younger ages-and relied on herbaceous angiosperm taxa with high rates of molecular evolution. Ages based on first and second codon positions of rbcL are markedly older than those based on third positions, which conflict with the fossil record in being too young, but all examined data partitions of rbcL and 18S depart substantially from a molecular clock. Age estimates are surprisingly insensitive to different views on seed-plant relationships. Randomization schemes were used to quantify confidence intervals due to phylogenetic uncertainty, substitutional noise, and lineage effects (deviations from a molecular clock). Estimates of the age of crown-group angiosperms range from 68 to 281 mya (million years ago), depending on data, tree, and assumptions, with most ∼140-190 mya (Early Jurassic-earliest Cretaceous). Approximate 95% confidence intervals on ages are wider for rbcL than 18S, ranging up to 160 my for phylogenetic uncertainty, 90 my for substitutional noise, and 70 my for lineage effects. These intervals overlap the oldest occurrences of angiosperms in the fossil record, as well as some estimates from previous molecular studies.
Among the plants collected from the Pie de Vaca Formation of the Oligocene, of Tepexi de Rodríguez, Puebla, México are five plants of Anacardiaceae, Haplorhus medranoensis, Rhus toxicodendron, Rhus sp., Comocladia intermedia, and Pistacia marquezii represented by their leaves and/or leaflets. The past and present diversity and geographic distribution of one of these genera, Rhus, demonstrate its capability to adapt and diversify in a wide variety of environments. Leaf architecture characters of this taxon overlap with those of other genera in the family, suggesting a high degree of phenotypic plasticity. The presence in the Pie de Vaca Formation of a type of Pistacia with leaf architecture characters similar to those of Asian plants further supports a long history of exchange between low-latitude North America and Asia. Links between low-latitude North and South America and the Caribbean are suggested by the presence of Comocladia and Haplorhus. Whereas Comocladia highlights the long history of regional endemics in the area, Haplorhus, today an endemic monotypic genus of Peru, suggests exchange mechanisms between North and South America. The morphologic characters of these taxa, and those of Pseudosmodingium (Anacardiaceae), some Rosaceae, Leguminosae, and Berberidaceae, suggest that the Pie de Vaca community was established and evolved in harsh environmental conditions. The Pie de Vaca flora thus provides significant new insights into the biogeographic relationships of the low latitude vegetation of North America.
In a recent analysis of the historical biogeography of Melastomataceae, Renner, Clausing, and Meyer (2001; American Journal of Botany 88(7): 1290-1300) rejected the hypothesis of a Gondwana origin. Using a fossil-calibrated chloroplast DNA (ndhF) phylogeny, they placed the early diversification of Melastomataceae in Laurasia at the Paleocene/Eocene boundary (ca. 55 Ma) and suggested that long-distance oceanic dispersals in the Oligocene and Miocene (34 to 5 Ma) account for its range expansion into South America, Africa, and Madagascar. Their critical assumption-that oldest northern mid-latitude melastome fossils reflect tribal ages and their geographic origins-may be erroneous, however, because of the sparse fossil record in the tropics. We show that rates of synonymous nucleotide substitutions derived by the Renner et al. (2001) model are up to three times faster than most published rates. Under a Gondwana-origin model advocated here, which includes dispersals from Africa to Southeast Asia via the "Indian ark" and emphasizes filter rather than either sweepstakes dispersal or strict vicariance, rates of nucleotide substitution fall within the range of published rates. We suggest that biogeographic reconstructions need to consider the paucity of Gondwanan fossils and that frequently overlooked interplate dispersal routes provide alternatives to vicariance, boreotropical dispersal, and long-distance oceanic dispersal as explanations for the amphi-oceanic disjunctions of many tropical rain forest plants.
Estimation of divergence times from sequence data has become increasingly feasible in recent years. Conflicts between fossil evidence and molecular dates have sparked the development of new methods for inferring divergence times, further encouraging these efforts. In this paper, available methods for estimating divergence times are reviewed, especially those geared toward handling the widespread variation in rates of molecular evolution observed among lineages. The assumptions, strengths, and weaknesses of local clock, Bayesian, and rate smoothing methods are described. The rapidly growing literature applying these methods to key divergence times in plant evolutionary history is also reviewed. These include the crown group ages of green plants, land plants, seed plants, angiosperms, and major subclades of angiosperms. Finally, attempts to infer divergence times are described in the context of two very different temporal settings: recent adaptive radiations and much more ancient biogeographic patterns.
Unlabelled:
Premise of the study:
It has been 8 years since the last comprehensive analysis of divergence times across the angiosperms. Given recent methodological improvements in estimating divergence times, refined understanding of relationships among major angiosperm lineages, and the immense interest in using large angiosperm phylogenies to investigate questions in ecology and comparative biology, new estimates of the ages of the major clades are badly needed. Improved estimations of divergence times will concomitantly improve our understanding of both the evolutionary history of the angiosperms and the patterns and processes that have led to this highly diverse clade. •
Methods:
We simultaneously estimated the age of the angiosperms and the divergence times of key angiosperm lineages, using 36 calibration points for 567 taxa and a "relaxed clock" methodology that does not assume any correlation between rates, thus allowing for lineage-specific rate heterogeneity. •
Key results:
Based on the analysis for which we set fossils to fit lognormal priors, we obtained an estimated age of the angiosperms of 167-199 Ma and the following age estimates for major angiosperm clades: Mesangiospermae (139-156 Ma); Gunneridae (109-139 Ma); Rosidae (108-121 Ma); Asteridae (101-119 Ma). •
Conclusions:
With the exception of the age of the angiosperms themselves, these age estimates are generally younger than other recent molecular estimates and very close to dates inferred from the fossil record. We also provide dates for all major angiosperm clades (including 45 orders and 335 families [208 stem group age only, 127 both stem and crown group ages], sensu APG III). Our analyses provide a new comprehensive source of reference dates for major angiosperm clades that we hope will be of broad utility.
The Amazonian rainforest is arguably the most species-rich terrestrial ecosystem in the world, yet the timing of the origin
and evolutionary causes of this diversity are a matter of debate. We review the geologic and phylogenetic evidence from Amazonia
and compare it with uplift records from the Andes. This uplift and its effect on regional climate fundamentally changed the
Amazonian landscape by reconfiguring drainage patterns and creating a vast influx of sediments into the basin. On this “Andean”
substrate, a region-wide edaphic mosaic developed that became extremely rich in species, particularly in Western Amazonia.
We show that Andean uplift was crucial for the evolution of Amazonian landscapes and ecosystems, and that current biodiversity
patterns are rooted deep in the pre-Quaternary.
Neotropical rainforests have a very poor fossil record, making hypotheses concerning their origins difficult to evaluate. Nevertheless, some of their most important characteristics can be preserved in the fossil record: high plant diversity, dominance by a distinctive combination of angiosperm families, a preponderance of plant species with large, smooth-margined leaves, and evidence for a high diversity of herbivorous insects. Here, we report on an approximately 58-my-old flora from the Cerrejón Formation of Colombia (paleolatitude approximately 5 degrees N) that is the earliest megafossil record of Neotropical rainforest. The flora has abundant, diverse palms and legumes and similar family composition to extant Neotropical rainforest. Three-quarters of the leaf types are large and entire-margined, indicating rainfall >2,500 mm/year and mean annual temperature >25 degrees C. Despite modern family composition and tropical paleoclimate, the diversity of fossil pollen and leaf samples is 60-80% that of comparable samples from extant and Quaternary Neotropical rainforest from similar climates. Insect feeding damage on Cerrejón fossil leaves, representing primary consumers, is abundant, but also of low diversity, and overwhelmingly made by generalist feeders rather than specialized herbivores. Cerrejón megafossils provide strong evidence that the same Neotropical rainforest families have characterized the biome since the Paleocene, maintaining their importance through climatic phases warmer and cooler than present. The low diversity of both plants and herbivorous insects in this Paleocene Neotropical rainforest may reflect an early stage in the diversification of the lineages that inhabit this biome, and/or a long recovery period from the terminal Cretaceous extinction.
A series of climate simulations using an atmospheric general circulation
model shows that maintaining ocean heat transport at close to
present-day values, but with otherwise glacial boundary conditions,
leads to an enhanced cooling, particularly in the tropics. This is in
agreement with recent geochemical evidence from fossil corals, ground
waters, and ice. Near-modern ocean heat transport may have been
sustained in all ocean basins during the Last Glacial Maximum in order
to balance the formation and export of Glacial North Atlantic
Intermediate Water.
Ice-sheet development in Antarctica was a result of significant and rapid global climate change about 34 million years ago. Ice-sheet and climate modelling suggest reductions in atmospheric carbon dioxide (less than three times the pre-industrial level of 280 parts per million by volume) that, in conjunction with the development of the Antarctic Circumpolar Current, led to cooling and glaciation paced by changes in Earth's orbit. Based on the present subglacial topography, numerical models point to ice-sheet genesis on mountain massifs of Antarctica, including the Gamburtsev mountains at Dome A, the centre of the present ice sheet. Our lack of knowledge of the present-day topography of the Gamburtsev mountains means, however, that the nature of early glaciation and subsequent development of a continental-sized ice sheet are uncertain. Here we present radar information about the base of the ice at Dome A, revealing classic Alpine topography with pre-existing river valleys overdeepened by valley glaciers formed when the mean summer surface temperature was around 3 degrees C. This landscape is likely to have developed during the initial phases of Antarctic glaciation. According to Antarctic climate history (estimated from offshore sediment records) the Gamburtsev mountains are probably older than 34 million years and were the main centre for ice-sheet growth. Moreover, the landscape has most probably been preserved beneath the present ice sheet for around 14 million years.
The evolutionary history of life includes two primary components: phylogeny and timescale. Phylogeny refers to the branching order (relationships) of species or other taxa within a group and is crucial for understanding the inheritance of traits and for erecting classifications. However, a timescale is equally important because it provides a way to compare phylogeny directly with the evolution of other organisms and with planetary history such as geology, climate, extraterrestrial impacts, and other features. The Timetree of Life is the first reference book to synthesize the wealth of information relating to the temporal component of phylogenetic trees. In the past, biologists have relied exclusively upon the fossil record to infer an evolutionary timescale. However, recent revolutionary advances in molecular biology have made it possible to not only estimate the relationships of many groups of organisms, but also to estimate their times of divergence with molecular clocks. The routine estimation and utilization of these so-called ‘time-trees’ could add exciting new dimensions to biology including enhanced opportunities to integrate large molecular data sets with fossil and biogeographic evidence (and thereby foster greater communication between molecular and traditional systematists). They could help estimate not only ancestral character states but also evolutionary rates in numerous categories of organismal phenotype; establish more reliable associations between causal historical processes and biological outcomes; develop a universally standardized scheme for biological classifications; and generally promote novel avenues of thought in many arenas of comparative evolutionary biology. This authoritative reference work brings together, for the first time, experts on all major groups of organisms to assemble a timetree of life. The result is a comprehensive resource on evolutionary history which will be an indispensable reference for scientists, educators, and students in the life sciences, earth sciences, and molecular biology. For each major group of organism, a representative is illustrated and a timetree of families and higher taxonomic groups is shown. Basic aspects of the evolutionary history of the group, the fossil record, and competing hypotheses of relationships are discussed. Details of the divergence times are presented for each node in the timetree, and primary literature references are included.
This book is a unique and integrated account of the history of North American vegetation and paleoenvironments over the past 70 million years. It includes discussions of the modern plant communities, causal factors for environmental change, biotic response, and methodologies. The history reveals a North American vegetation that is vast, immensely complex, and dynamic.
A fossil flora from the Late Paleocene-Early Eocene Thyra Ø Formation of eastern North Greenland (paleolatitude 77° N) has yielded monocotyledon leaf impressions with characters seen only in the closely related modem species in the families of Heliconiaceae, Musaceae, and Strelitziaceae. The combination of large costae widths and parallel, nonanastomosing, lateral veins that depart at right angles from the costae in the fossil material are features present only in leaves of extant species from these families. Three basic venation patterns also are recognized in the modem species of these families, but except for the genera Strelitzia and Phenakospermum, none of these patterns are present exclusively in any one family. Musopsis n. gen. is created for the fossil material from Greenland, but it is considered a form genus due to the lack of gross morphological features that can be used for separating leaves of the modem genera in Heliconiaceae, Musaceae, and Strelitiziaceae. It is the first known Arctic occurrence of fossil leaf material resembling this modem group of taxa.
In Plants and the K-T Boundary, two of the world's leading experts in palynology and paleobotany provide a comprehensive account of the fate of land plants during the ‘great extinction’ about 65 million years ago. They describe how the time boundary between the Cretaceous and Paleogene Periods (the K-T boundary) is recognized in the geological record, and how fossil plants can be used to understand global events of that time. There are case studies from over 100 localities around the world, including North America, China, Russia and New Zealand. The book concludes with an evaluation of possible causes of the K-T boundary event and its effects on floras of the past and present. This book is written for researchers and students in paleontology, botany, geology and Earth history, and everyone who has been following the course of the extinction debate and the K-T boundary paradigm shift.
The book focuses on geological history as the critical factor in determining the present biodiversity and landscapes of Amazonia. The different driving mechanisms for landscape evolution are explored by reviewing the history of the Amazonian Craton, the associated sedimentary basins, and the role of mountain uplift and climate change. This book provdes an insight into the Meso- and Cenozoic record of Amazonia that was characterized by fluvial and long-lived lake systems and a highly diverse flora and fauna. This fauna includes giants such as the ca. 12 m long caiman Purussaurus, but also a varied fish fauna and fragile molluscs, whilst fossil pollen and spores form relics of ancestral swamps and rainforests. Finally, a review the molecular datasets of the modern Amazonian rainforest and aquatic ecosystem, discussing the possible relations between the origin of Amazonian species diversity and the palaeogeographic, palaeoclimatic and palaeoenvironmental evolution of northern South America. The multidisciplinary approach in evaluating the history of Amazonia has resulted in a comprehensive volume that provides novel insights into the evolution of this region.
Paleogene, Maastrichtian, and Miocene floras are reviewed. They are located on continental margins, where several sedimentary basins developed. The affinities of the fossil genera to living ones allow the recognition of three paleofloras: Neotropical, Mixed, and Antarctic. These could be the forerunners, respectively, of the presently more humid dominions in Neotropical Region (Caribbean, Amazonic, and Guayano), of the drier ones (Chaqueno and Andino-Patagonico), and of the Subantarctic Dominion of the Antarctic Region. The South American climate, as indicated by the fossil floras, showed a trend to higher temperatures during the Paleocene and Lower Eocene, and a deterioration through the Middle and Upper Eocene.
Palynological data emphasize the presence of two distinctive provinces during the Late Cretaceous, one including eastern North America and Europe and a second including the major part of Asia and western North America. The distinction between these two provinces became increasingly blurred during the Paleogene. During the Eocene, the ram forests of both Europe and western North America shared numerous genera, both extinct and extant. The great majority of the latter and most of the closest extant relatives of the former now occur in the Indomalayan region. It is thus clear that much of the present Indomalayan flora represents a relict of a once widespread Northern Hemisphere tropical (s.l.) flora, one that has largely (but not entirely) been eliminated from the New World. Among the possible New World survivors of this boreotropical flora are some of the dry Caribbean genera, which could have been derived from lineages of the dry tropical vegetation of the Gulf Coast Eocene; only a handful of present Neotropical lowland rain forest genera appear to be boreotropical relicts.
The modern New Zealand angiosperm flora has many notable characteristics, such
as a predominance of evergreen, perennial life forms, few nitrogen-fixing
species, despecialised floral features and asymmetric genus—species
relations. The origin of these features has been attributed to antiquity of
the flora, isolation and/or environmental history. Using evidence from
palynology and macrofossils, we investigate the characteristics of the
mid–late Cenozoic angiosperm flora and the impact of environmental
changes in land area and configuration, physiography and climate on the
depletion and composition of the New Zealand flora. Climatic cooling,
increasing isolation and tectonism have each acted as important environmental
filters, contributing to regional extinctions and decreasing floral diversity,
and inducing major turnover in the floristic composition of New Zealand.
During the Miocene and Pliocene at least 15 families and a minimum of 36
genera were lost from the New Zealand flora. These included a range of life
forms and physiognomically important taxa such as
Acacia, Bombax,
Casuarina, Eucalyptus,
Ilex, many Proteaceae and several palms. The extinction
and decline in richness of subtropical families was caused by the onset of
cooling conditions in the Late Miocene—Pliocene, and exacerbated by
the absence of significant land areas to act as refugia at lower latitudes.
Many of these genera/families persist today on islands to the north (e.g.
New Caledonia), reflecting mid-Cenozoic land conduits, and in Australia. The
close floristic links with New Caledonia were probably maintained by
intermittent island stepping-stones which facilitated interchange of
subtropical taxa until the Late Miocene. The Pleistocene extinction of some
genera, tolerant of warm-temperate environments (e.g.
Acacia, Eucalyptus) may be a
reflection of the fact that persistent mesic conditions favoured widespread
dominance of dense rainforest during interglacials. The loss of these groups,
containing diverse life forms and floral structures, suggests that many of the
present characteristics of the New Zealand flora reflect strong selective
pressures, mainly driven by climate change, in the Late Miocene, Pliocene and
Pleistocene, rather than events of greater geological antiquity.
The isolation of South America from Central America and Africa during the Tertiary Period left a strong imprint on the flora of the Neotropics. South American Eocene through Miocene fossil assemblages, both pollen and macrofossils, document a rich tropical flora on the continental margins, and represent some of the only data on pre-landbridge lowland taxa in South America. Lowland Miocene floras from Amazonia are remarkably similar in their high diversity to Amazonian floras today based on lists of dominant families. Recent geophysical data on the uplift of the northern Andes show a strong correlation between uplift and the development and diversification of montane forests in Colombia and Venezuela. The emergence of a continuous landbridge at 3 Ma between Central and South America is well documented and is demonstrated by the arrival of temperate elements in South American highlands and concurrent appearance of South American taxa in Central America. There is no evidence for displacement of lowland tropical plants in South America by northern immigrants, which appears to stand in contrast to the published record for mammals. The mix of taxa in extant Mexican tropical floras derived from tropical South America, tropical Central America, and from remnants of northern tropical Eocene floras is strong evidence for the impact that the landbridge through the Panamanian isthmus had on the neotropical flora. The early appearance of low-elevation savannas is inferred from an increase in grass pollen in the middle Pliocene of Panama; however, widespread savannas are not indicated by pollen data from the Central American region. Rather, beginning in the latest Miocene Epoch and continuing up to the Quaternary, a mix of tropical rainforest and mixed tropical woodlands is suggested for the lowlands, based on pollen evidence. Accumulating data on temperature changes during the late Tertiary and Quaternary Periods points to low-latitude temperature fluctuations of up to 6 degrees C. Proposals of accompanying widespread rainfall fluctuations are more equivocal. Rainfall probably varied regionally, resulting in a mosaic of habitats controlled by river migration, sea level fluctuations. local dryness, and local uplift. Zones postulated as refugia provide testable hypotheses using neoecological and paleoecological data. The paleoecological data to test three hypotheses are still limited taxonomically and spatially. It is important to stress that the effect of the isolation of South American neotropical floras has not been erased in the 3 million years since their connection with Central America. New data front middle and late Miocene floras in South America will be critical in determining the degree to which the composition of South American floras has been influenced by immigration of plants from the better-known Central American area to the north.
Palynological records from the Western Portuguese and Algarve basins (Portugal) provide new insights on the timing and pattern of the early diversification of angiosperms (flowering plants) and its relationship to global environmental perturbations during the late Early Cretaceous. Angiosperm pollen displays a stepwise increase in both diversity and relative abundance during the late Barremian to middle Albian interval (ca. 124 104 Ma), reflecting the incipient radiation of flowering plants in lower midlatitude floras. Our results provide new evidence for the age interpretation of the previously described angiosperm mesofossil floras and associated in situ pollen assemblages from the Western Portuguese basin, until now interpreted as Barremian or possibly Aptian in age. Biostratigraphic and sedimentologic evidence indicates a post-Aptian age for these assemblages, hence demonstrating a major radiation phase of angiosperms during the early Albian. Correlation of the angiosperm pollen record with data on global paleoenvironmental changes suggests a link between the rapid adaptive radiation of flowering plants and major climatic and oceanographic perturbations during the late Early Cretaceous.
Geological events of biological importance in the history of the Andes include their impact on global climates through an influence on atmospheric circulation, rainfall patterns, and the atmospheric concentration of CO2; habitat diversification from lowlands through páramo to glaciated peaks; and migratory pathways ranging from discontinuous (mesic elements), highly discontinuous (páramo elements), barriers (to east-west migrations), to selective pathways (via the dry Andean valleys). The timing of these effects is a function of the uplift history of three (to nine) morphotectonic segments of the Andes resulting in (1) mostly lowland swamp and fluvial environments in the Cretaceous and Paleocene, (2) moderate uplands beginning in the Late Eocene (ca. 40 million years ago [Ma]), (3) appression of an offshore volcanic chain (the proto–Cordillera Occidental) in the Oligocene (ca. 30 Ma), (4) uplift of the proto–Cordillera Oriental and the Altiplano to about half their present altitude by the Middle Miocene (ca. 15 Ma), and (5) uplift of the remaining half within approximately the past 10 million years. The early appearance of a biological community recognizable as the Atacama Desert is estimated at ca. 15 Ma, and the beginnings of a páramo at ca. 3.5 Ma. Longer-term (Milankovitch) and shorter-term (Younger Dryas, Medieval warm/dry period, Little Ice Age, Heinrich, and Dansgaard-Oeschger [D-O]) climatic events, known initially from the high latitudes, are now widely recognized throughout Latin America, including the Andes. They document a dynamic physical environment from the Cretaceous through the Holocene and on all timescales.
Fossils of 134 taxa attributed to the Rubiaceae are described or mentioned in 115 publications dating from 1850 and from deposits as old as the Cretaceous and Paleocene. Close scrutiny of these records indicates, however, that the oldest and most likely (accepted) representatives of the family are four genera, Emmenopterys Oliv. from the Middle Eocene of Oregon and Washington, U.S.A., Faramea Aubl. from the Late Eocene of Panama, and Guettarda L. (cf. as †Guettardidites; †= fossil taxon) and Canthium Lam. (as †Rubipollis oblatus) from the Late Eocene of Australia, and a probable fifth genus, the alternate-leaved †Paleorubiaceophyllum eocenicum from the Middle Eocene of Tennessee/Kentucky, U.S.A. The record represents three subfamilies (Rubioideae, Ixoroideae, Cinchonoideae) from three widely separated geographic regions, implying an earlier origin in the Late Cretaceous or Paleocene. From the Oligocene, there are six accepted genera, Coprosma J. R. Forst. & G. Forst., Coprosma–Opercularia, Faramea Aubl., Macrosphyra Hook. f. (as †Triporotetradites hoekeni), Mitragyna Korth. (as †Retitricolporites annulatus), and Pinckneya Michx. from Africa (Cameroon), Australia and New Zealand, U.S.A. (Oregon), and Puerto Rico. The period of greatest diversification and radiation was in the Miocene, with 20 accepted genera reported from North America, Central America, South America, Southeast Pacific–Asia, Africa, and Europe. Stages in the evolution of three characters are further suggested by the fossil record. The relatively uncommon occurrence of alternate leaves among modern taxa is typical of advanced genera (e.g., Didymochlamys Hook. f., Sabicea Aubl., Theligonum L.), but this feature may have already developed by the Middle Eocene (†Paleorubiaceophyllum). Polyploidy is suggested in the Middle Eocene P. eocenicum var. lawrensis by epidermal cells 32 µm in diameter or nearly twice the size of the other varieties. Pollen polymorphism, possibly coordinated with or as a prelude to heterostyly, is represented by the diporate pollen of Faramea in the Late Eocene, and triporate and tetraporate forms in the Miocene and Pliocene. Currently, the principal needs are: (1) to clarify pending Paleocene records of †Cinchonidium (Cinchona L.), North Dakota, U.S.A.; Galium L., Greenland; and †Psilatricolpites coprosmoides (Coprosma, Chile); and (2) to examine the several large Cretaceous megafossil floras now under study (e.g., Anfiteatro de Ticó, Argentina; Crato, Brazil; Turonian-age floras, New Jersey and Sweden) for specimens with features that suggest a rubiaceous complex or with an aggregation of features suggesting presence of the family.
The Cenozoic Quillagua–Llamara basin (northern Chile, Central Andes) is an asymmetrical, intramassif fore-arc basin with a relatively wide northern sector separated from a narrower southward extension by a basement threshold. The northern sector was characterised by a noticeable Oligocene?–late Neogene alluvial-fan and lacustrine dominated deposition which resulted in sequences up to 900 m thick, whereas the southern sector was often a bypass zone with thinner fluvial and lacustrine sediment accumulation. The basin infill includes two third-order alluvial–lacustrine unconformity-bounded units which include other higher-frequency (4th to 5th order) sequences. The evolution of the Late Miocene–Pliocene lacustrine episodes in the Quillagua–Llamara basin was not only controlled by the regional variations from arid to hyperarid palaeoclimate conditions, due to the combined influence of the Pacific high pressure cell, the rain shadow effect exerted by the rising Andes and the northward flowing cold oceanic currents, but also by: (a) the extensional tectonics and evolution and uplift of the fore-arc region which defined the location and size of the depocentres; (b) the resulting basement palaeorelief which affected sediment thickness and facies distribution during the late basin-infill episodes; and (c) the tectonic modifications of watersheds, water divides and drainage networks in the Precordillera which caused considerable changes of water income in the lacustrine systems. Understanding of this regional tectonosedimentary evolution is a necessary first step before analysing of the low- to high-order lacustrine sequence changes in the region. Lacustrine water supply was very sensitive to tectonics; even gentle tectonic tilting and uplifting in critical water-divide zones could result in changes in water balance in the lacustrine basins and trigger variations in the depositional record. The very conspicuous, lacustrine regime changes recorded in the Quillagua–Llamara basin infill cannot be considered in themselves conclusive proof of an exclusive climatic forcing, since they took place close to either major regional drainage changes or to gentle but noticeable tectonic reactivation in the fore-arc region.
The oldest and northernmost record of the tapir lineage, Thuliadanta mayri gen. et sp. nov. from Ellesmere Island, Arctic Canada (78°50′N) implies that tapiroid evolution was well underway by early Eocene (Wasatchian) time in northern high latitudes, and raises the possibility of a North American origin for the group. Phylogenetic analyses place the new Arctic tapir as the sister group to the later more advanced Desmatotherium, Colodon, and Irdinolophus. A phylogenetically-derived biogeographic reconstruction posed here suggests the tapir lineage may represent a rare instance of counterflow wherein an exotic North American taxon invaded Asia during the early Eocene. Moreover, Thuliadanta seems a plausible ancestor to Desmatotherium from both continents, suggesting that this branch of the tapir lineage may have originated at high latitudes and subsequently dispersed from there to mid-latitudes. Thuliadanta's occurrence on Ellesmere Island indicates that northern high latitudes should also be evaluated as a potential source area for some of the exotic taxa appearing in mid-latitudes during Eocene time. Using today's tapirs, and specifically the mountain tapir, as analogs, Thuliadanta seems a plausible year-round inhabitant in the mild temperate lowland forests of the Eocene High Arctic.
—Rhexia, with 11 species in the Coastal Plain province of North America, is the only temperate zone endemic of the tropical eudicot family Melastomataceae. It is a member of the only pantropical tribe of that family, Melastomeae. Based on the chloroplast gene ndhF, we use a fossil-calibrated molecular clock to address the question of the geographic origin and age of Rhexia. Sequences from 37 species in 21 genera representing the tribe's geographical range were analyzed together with five outgroups. To obtain better clade support, another chloroplast region, the rpll6 intron, was added for 24 of the species. Parsimony analysis of the combined data and maximum-likelihood analysis of ndhF alone indicate that the deepest split is between Rhexia plus its sister group, a small Central American genus, and all other Melastomeae. Old World Melastomeae are monophyletic and nested within New World Melastomeae. Although likelihood-ratio tests of clock and nonclock substitution models for the full or moderately pruned datasets rejected the clock, these models yielded identical topologies (for 30 taxa) with few significantly different branch lengths as assessed by a Student's t-test. Age estimates obtained were 22 million years ago (Mya) for the divergence of Rhexia from its sister group, 12 Mya for the dispersal of Melastomeae from the New World to West Africa, and 1 Mya for the diversification of Melastoma in Southeast Asia. The only other genus of Melastomeae to have reached Southeast Asia from Africa or Madagascar is Osbeckia. The age and geographic distribution of fossils, which come from Miocene sites throughout Eurasia, suggest that Melastomeae once ranged from Eurasia across Beringia to North America from whence they reached South America and subsequently Africa and Southeast Asia. Climate deterioration led to their extinction in the Northern Hemisphere, with Rhexia possibly surviving in Coastal Plain refugia.
When compared to a database of modern foliar physiognomy and climate, the physiognomy of a new collection of dicotyledonous leaves from the 10.66 ± 0.06 Ma Jakokkota flora, Bolivian Altiplano, implies a mean annual temperature (MAT) of 18.6-21.0 ± 2.5°C. Similarly, a literature-derived sample of the early-middle Miocene Potosi flora, Cordillera Oriental, implies a MAT of 21.5-21.7 ± 2.1°C. We estimate that both floras experienced a growing season precipitation of 50 ± 40 cm. The paleoclimate thus appears considerably warmer than the current highland climate, with MATs of 8-9°C; the paleoprecipitation is indistinguishable from modern levels. A comparison of the Miocene MATs with the modern MATs, with the effects of latitudinal continental drift and global climate change subtracted, suggests that the Jakokkota flora grew at an elevation of 590-1610±1000 m, and the Potosi flora grew at an elevation of 0-1320 ± 1000 m. Both paleoelevation estimates are significantly lower than the present elevations of 3940 and 4300 m, respectively, requiring a substantial component of Andean uplift since 10.7 Ma. This uplift history is consistent with two-stage tectonic models of Andean orogeny.
The evolution of grasses using C4 photosynthesis and their sudden rise to ecological dominance 3 to 8 million years ago is among the most dramatic examples
of biome assembly in the geological record. A growing body of work suggests that the patterns and drivers of C4 grassland expansion were considerably more complex than originally assumed. Previous research has benefited substantially
from dialog between geologists and ecologists, but current research must now integrate fully with phylogenetics. A synthesis
of grass evolutionary biology with grassland ecosystem science will further our knowledge of the evolution of traits that
promote dominance in grassland systems and will provide a new context in which to evaluate the relative importance of C4 photosynthesis in transforming ecosystems across large regions of Earth.
Quantifying atmospheric CO(2) concentrations ([CO(2)](atm)) during Earth's ancient greenhouse episodes is essential for accurately predicting the response of future climate to elevated CO(2) levels. Empirical estimates of [CO(2)](atm) during Paleozoic and Mesozoic greenhouse climates are based primarily on the carbon isotope composition of calcium carbonate in fossil soils. We report that greenhouse [CO(2)](atm) have been significantly overestimated because previously assumed soil CO(2) concentrations during carbonate formation are too high. More accurate [CO(2)](atm), resulting from better constraints on soil CO(2), indicate that large (1,000s of ppmV) fluctuations in [CO(2)](atm) did not characterize ancient climates and that past greenhouse climates were accompanied by concentrations similar to those projected for A.D. 2100.
Global temperatures have covaried with atmospheric carbon dioxide (CO2) over the last 450 million years of Earth’s history (1). Critically, ancient greenhouse periods provide some of the most pertinent information for anticipating how the Earth will respond to the current anthropogenic loading of greenhouse gases. Paleo-CO2 can be inferred either by proxy or by the modeling of the long-term carbon cycle. For much of the geologic past, estimates of CO2 are consistent across methods (1). One exception is the paleosol carbonate proxy, whose CO2 estimates are often more than twice as high as coeval estimates from other methods (1). This discrepancy has led some to question the validity of the other methods and has hindered attempts to understand the linkages between paleo-CO2 and other parts of the Earth system. In this issue of PNAS, Breecker and colleagues (2) break important new ground for resolving this conflict.