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Rosaceous Chamaebatiaria-Like Foliage from the Paleogene of Western North America
Abstract
Chamaebatiaria and Chamaebatia, two characteristic genera of the Californian floristic province, are traditionally placed in different subfamilies of Rosaceae, Spiraeoideae and Rosoideae, respectively. Analysis of the foliar and reproductive characters of the extant species of these genera indicates that the two genera could be closely related and the assignment of Chamaebatia to Rosoideae invalid. Fossil leaves of lineages of both genera occur in the Paleogene montane floras of the Rocky Mountain region and provide evidence that the two lineages diverged from a common ancestor in the Eocene. The common ancestor probably was adapted to sunny habitats in mesic coniferous forest, and, during the post-Eocene, the two lineages were able to adapt to progressively drier climates. A third extant genus, the east Asian Sorbaria, also appears to be closely related to the California genera and to have been derived from the same common ancestor. New taxa and combinations proposed are: Stonebergia columbiana, n. gen. and n. sp.; Salmonensea prefoliolosa (R. W. Br.), n. gen. and n. comb.; Stockeya creedensis (R. W. Br.), n. gen. and n. comb.; Stockeya montana, n. sp.; and Sorbaria wahrhaftigii, n. sp. -Authors
... Kvaček et al. (1994) suggested a possible affinity to Sorbus, although they ultimately left the genus and species unassigned. This morphotype also closely resembles fossils assigned to Sorbaria from late Eocene/early Oligocene and Miocene deposits in Alaska (Wolfe & Tanai 1980;Wolfe & Wehr 1988). Damage to the specimen obscures whether the leaflets are paracompound and lacking intersecondary laminar segments (i.e., Sorbaria), or pinnatisect with intersecondary laminar segments, which would suggest a more primitive systematic position (e.g., Stonebergia J.A.Wolfe et Wehr; Wolfe & Wehr 1988). ...
... This morphotype also closely resembles fossils assigned to Sorbaria from late Eocene/early Oligocene and Miocene deposits in Alaska (Wolfe & Tanai 1980;Wolfe & Wehr 1988). Damage to the specimen obscures whether the leaflets are paracompound and lacking intersecondary laminar segments (i.e., Sorbaria), or pinnatisect with intersecondary laminar segments, which would suggest a more primitive systematic position (e.g., Stonebergia J.A.Wolfe et Wehr; Wolfe & Wehr 1988). ...
... Sorbus wahrhaftigii J.A.Wolfe et Wehr from the late Eocene/early Oligocene Rex Creek flora in Alaska can be recognized based on the presence of laminar hairs, tertiary vein pairs, laminar size, and the number of subsidiary teeth on the apical and basal flanks of major teeth (Wolfe & Wehr 1988). The Ellesmere Island morphotype is described from a single incomplete specimen that is poorly preserved (e.g., tertiary venation not visible). ...
Understanding the causal mechanisms of the modern latitudinal diversity gradient (LDG) is a long-established problem in ecology. Temperature has been proposed as the primary driver of the modern LDG, although other hypotheses (e.g. precipitation, insolation, seasonality, biogeographical history, and biological interactions), have been suggested as constraints or drivers of diversity in the extra-tropics (i.e. the mid- and high-latitudes). The modern Arctic is characterized by very low floral diversity and a cold dry climate; however, the early Eocene Arctic was much warmer and wetter, as evidenced from paleobotanical climate reconstructions (e.g. MAT ≈ 8.5–12.7 ºC and MAP >150 cm/yr), and the presence of thermophilic flora and fauna (e.g. palm or palm-like palynomorphs and alligators). Nevertheless, forest diversity for Arctic Eocene ecosystems remains relatively untested and is typically described as low and homogenous. Reported here are the first quantitative megafloral diversity estimates from Stenkul Fiord, Ellesmere Island, Canada, utilizing two purpose-made census-sampled fossil leaf collections coupled with horizon-specific palynological analyses. Recent U-Pb zircon geochronology, and new geological mapping at Stenkul Fiord, place the fossil sites stratigraphically near the PETM and ETM2 hyperthermal events of the early Eocene, a time when warm equable climates allowed temperate and tropical plant taxa to survive at high northern latitudes. Diversity was assessed using coverage-based interpolation- and extrapolation-based rarefaction, a method that reconstructs richness with high accuracy. The results show that the early Eocene paleoarctic forests supported diverse forest ecosystems with floral diversity similar to modern mid-latitude mesic-mesothermal broadleaf forests from North America, but overall floral diversity may have been restricted as a result of photic seasonality. Furthermore, these ecosystems experienced floristic change probably related to the transient hyperthermal events.
... Kvaček et al. (1994) suggested a possible affinity to Sorbus, although they ultimately left the genus and species unassigned. This morphotype also closely resembles fossils assigned to Sorbaria from late Eocene/early Oligocene and Miocene deposits in Alaska (Wolfe & Tanai 1980;Wolfe & Wehr 1988). Damage to the specimen obscures whether the leaflets are paracompound and lacking intersecondary laminar segments (i.e., Sorbaria), or pinnatisect with intersecondary laminar segments, which would suggest a more primitive systematic position (e.g., Stonebergia J.A.Wolfe et Wehr; Wolfe & Wehr 1988). ...
... This morphotype also closely resembles fossils assigned to Sorbaria from late Eocene/early Oligocene and Miocene deposits in Alaska (Wolfe & Tanai 1980;Wolfe & Wehr 1988). Damage to the specimen obscures whether the leaflets are paracompound and lacking intersecondary laminar segments (i.e., Sorbaria), or pinnatisect with intersecondary laminar segments, which would suggest a more primitive systematic position (e.g., Stonebergia J.A.Wolfe et Wehr; Wolfe & Wehr 1988). ...
... Sorbus wahrhaftigii J.A.Wolfe et Wehr from the late Eocene/early Oligocene Rex Creek flora in Alaska can be recognized based on the presence of laminar hairs, tertiary vein pairs, laminar size, and the number of subsidiary teeth on the apical and basal flanks of major teeth (Wolfe & Wehr 1988). The Ellesmere Island morphotype is described from a single incomplete specimen that is poorly preserved (e.g., tertiary venation not visible). ...
The late Paleocene to early Eocene sediments of Ellesmere and Axel Heiberg islands, Nunavut, of the Canadian High Arctic contain a rich fossil flora and fauna. Although the megafloral fossils have been known for more than a century, limited descriptions of the fossil flora have been presented. Here, we provide a comprehensive morphotype catalogue of fossil plants from multiple localities from Ellesmere and Axel Heiberg islands that form a systematic framework for establishing an early Paleogene polar flora from High Arctic latitudes in Canada. Described are 62 ‘dicot’ angiosperm morphotypes, three monocotyledonous angiosperms, 13 gymnosperms, and five pteridophyte morphotypes. This work presents a significant contribution to the understanding of north-polar diversity and environments during the warm greenhouse climate of the early Paleogene.
... Rosaceae have a long geologic history with all four subfamilies well represented in the fossil record by the Eocene (Wolfe and Wehr, 1988). Although there have been reports of Cretaceous Prunus leaves and fruits, these fossils need to be reinvestigated (Dilcher, 1974). ...
... Remains of Rosa L. (Rosoideae) from Paleocene or Eocene sediments, on the other hand, seem to have a reliable fossil record (Becker, 1963). Megafossils related to Maloideae and Spiraeoideae are abundant in Eocene deposits of the Pacific northwestern United States and southwestern Canada (Wolfe and Wehr, 1988). Several leaves have been referred to Maloideae (Wolfe and Wehr, 1988), but none of these fossils can be related to the five-carpellate, bi-ovulate plants of extant Maloideae. ...
... Megafossils related to Maloideae and Spiraeoideae are abundant in Eocene deposits of the Pacific northwestern United States and southwestern Canada (Wolfe and Wehr, 1988). Several leaves have been referred to Maloideae (Wolfe and Wehr, 1988), but none of these fossils can be related to the five-carpellate, bi-ovulate plants of extant Maloideae. Fossil leaves of Spiraeoideae include Spiraea and Holodiscus (Wolfe and Wehr, 1988). ...
Reinvestigation of the holotype and paratypes, as well as four new flowers of Paleorosa similkameenensis Basinger, have provided additional morphological and anatomical features to further characterize this early rosaceous flower. Noted features include the presence of a follicular fruit composed, at least in part, of thick-walled cells, seeds with possible remnants of embryonic tissue and hypostase, and pollen morphology and ultrastructure. The fruit is a follicle enclosed by a non-fleshy floral cup. Based on this fruit type Paleorosa is assigned to the Spiraeoideae. Although fruit morphology strongly supports inclusion of Paleorosa in Spiraeoideae, floral structure such as short, post-chalazal branching of the raphe and pollen morphology show similarities to Maloideae, particularly the genus Pyracantha Roemer. Paleorosa pollen is prolate and tricolporate with indistinct pores. The exine is striate, semi-tectate/columellate, and the sexine is thicker than the nexine. The intermediate characters of Paleorosa add strength to the hypothesis that Spiraeoideae may be ancestral to Maloideae. In addition, these intermediate characters provide further evidence for an important radiation of Rosaceae during the Eocene. This fossil material provides the opportunity to understand the pollen structure of the Rosaceae from the Eocene.
... Eocene forms are close to, but perhaps not exactly like, extant genera; and (3). Extinct genera with affinities at higher taxonomic levels, such as Paleorosa Basinger (Basinger 1976, Cevallos-Ferriz et al. 1993) and Stonebergia Wolfe & Wehr (Wolfe and Wehr 1988) which combine characters of several genera or even traditionally recognized subfamilies. It is not unusual for both extant and extinct taxa to be found side by side in fossil floras of Eocene age (DeVore et al. 2004). ...
... Stonebergia Wolfe & Wehr (Fig. 14), an extinct genus in the Chamaebatiaria (Porter) Maxim. complex is first recognized in the Eocene (Wolfe and Wehr 1988). Additional extinct genera in this group (Stockeya Wolfe and Wehr, Eleopoldia Wolfe and Wehr) were named from later Eocene and Oligocene floras (Wolfe and Wehr 1988). ...
... Eocene forms are close to, but perhaps not exactly like, extant genera; and (3). Extinct genera with affinities at higher taxonomic levels, such as Paleorosa Basinger (Basinger 1976, Cevallos-Ferriz et al. 1993) and Stonebergia Wolfe & Wehr (Wolfe and Wehr 1988) which combine characters of several genera or even traditionally recognized subfamilies. It is not unusual for both extant and extinct taxa to be found side by side in fossil floras of Eocene age (DeVore et al. 2004). ...
... Stonebergia Wolfe & Wehr (Fig. 14), an extinct genus in the Chamaebatiaria (Porter) Maxim. complex is first recognized in the Eocene (Wolfe and Wehr 1988). Additional extinct genera in this group (Stockeya Wolfe and Wehr, Eleopoldia Wolfe and Wehr) were named from later Eocene and Oligocene floras (Wolfe and Wehr 1988). ...
Many of the oldest definitive members of the Rosaceae are present in the Eocene upland floras of the Okanogan Highlands of
northeastern Washington State and British Columbia, Canada. Over a dozen rosaceous taxa representing extant and extinct genera
of all four traditionally recognized subfamilies are known from flowers, fruits, wood, pollen, and especially leaves. The
complexity seen in Eocene Rosaceae suggests that hybridization and polyploidy may have played a pivotal role in the early
evolution of the family. Increased species diversity and the first appearance of additional modern taxa occur during the Late
Paleogene in North America and Europe. The Rosaceae become increasingly important components of fossil floras during the Neogene,
with taxa adapted to many habitats.
... Rapse´and Kohn (2002) observed that S-alleles in four genera of Pyrinae appeared to have coalesced much more recently than those in genera of Solanaceae. These patterns suggest a rapid, ancient radiation or cladogenesis, which is consistent with the fossil record of several genera of Pyrinae from the early middle Eocene, 48-50 million years ago (Wolfe and Wehr 1988). Rapid, ancient radiations (also called starburst speciation) are a difficult challenge to phylogenetic inference (Donoghue and Sanderson 1992, Fishbein et al. 2001, Fishbein and Soltis 2004, Rokas et al. 2005 because short interior branches limit the historical record of early diversification. ...
... A rapid, ancient radiation of Pyrinae appears to be recorded by fossil data. Wolfe and Wehr (1988) observed that Rosaceae underwent ''a major generic-level diversification during the Eocene'' in northwestern North America. Fossils of Amelanchier, Crataegus and Photinia as well as close relatives of Malus and Sorbus are known from the early middle Eocene (48-50 million years ago); Heteromeles and Sorbus appeared later in the Eocene. ...
Generic relationships in the Pyrinae (equivalent to subfamily Maloideae) were assessed with six chloroplast regions and five
nuclear regions. We also plotted 12 non-molecular characters onto molecular phylogenies. Chloroplast DNA trees are incongruent
with those from nuclear regions, as are most nuclear regions with one another. Some of this conflict may be the result of
hybridization, which occurs between many genera of Pyrinae in the present and may have occurred in the past, and duplication
of nuclear loci. Sequence divergence between genera of Pyrinae, which is significantly less than that between genera of another
large clade in Rosaceae, the Rosoideae, is concentrated in terminal branches, with short internal branches. This pattern is
consistent with an ancient, rapid radiation, which has also been hypothesized from the fossil record. Even with about 500,000
bp of sequence, our results resolve only several small groups of genera and leave much uncertainty about phylogenetic relationships
within Pyrinae.
... Calibration was constrained with a minimum age of 44 million years ago (the Late Eocene; DeVore and Pigg, 2007), which is the approximate age of the stem group, i.e., the MRCA of the Pyrodae (including Aronia, Malus, Amelanchier, and Crataegus) and its sister clade containing members of the tribe Neillieae in the Spiraeoideae (Oh and Potter, 2005;Potter et al., 2007). For the stem group of Crataegus, we constrained the minimum age to be 25 mya according to the fossil leaves and fruits record (Oligocene; MacGinitie, 1933;Oliver, 1934;Lamotte, 1952;Hickey, 1984;Wolfe and Wehr, 1988;De-Vore and Pigg, 2007), assuming that fossils of the stem lineages leading to the crown group of Crataegus should be older than the fossil age of Crataegus itself. Confidence intervals of divergence time were further estimated by the non-parametric bootstrap procedure (Baldwin and Sanderson, 1998;Sanderson and Doyle, 2001). ...
... Moreover, most species of the sister genus of Crataegus, Amelanchier (and its segregate genera Malacomeles and Peraphyllum), as well as the other basal genera of the Pyrodae (e.g., Kageneckia, Lindleya, Vauquelinia, and Gillenia) are found today only in the New World . An extensive rosaceous fossil record in North America and Europe, from the Eocene onwards (DeVore and Pigg, 2007), in addition to the earliest evidences of Crataegus fossil from the Okanogan Highlands in North America in at least the late Oligocene (MacGinitie, 1933;Oliver, 1934;Lamotte, 1952;Hickey, 1984;Wolfe and Wehr, 1988;DeVore and Pigg, 2007) support Mesquite and DIVA results in our present study. ...
Phylogeographic relationships were constructed for 72 Old and New World Crataegus species using combinations of four chloroplast and up to five nuclear regions. Maximum parsimony, maximum likelihood, and Bayesian results yield consistent relationships among major lineages. The close associations of the East Asian and western North American species point toward ancient trans-Beringian migrations. Relationships among eastern North American species are poorly resolved and few groups are identified that are congruent with existing classifications. Scant variation and short internal branches among these species suggest rapid divergence associated with polyploidy and hybridization. Incongruence between the chloroplast and nuclear data, and morphology suggest hybrid origins of three species from an extinct European lineage (the male parent) and three different North American female parents. Europe and eastern North America are suggested as the most recent common areas for Crataegus; at least four dispersal events are inferred to explain the present distribution of the genus.
... The divergence times of 17 Crataegus and Amelanchier accessions were estimated. One constraint was based on the oldest fossil record of Amelanchier leaves from the Middle Eocene, or approximately 40 Mya, around One Mile Creek, Princeton, British Columbia (Wolfe and Wehr 1988). Another constraint was that Amelanchier and Crataegus were expected to have differentiated from each other around 45 Mya (Lo and Donoghue 2012). ...
Crataegus bretschneideri C. K. Schneid. is one of the species cultivated in China. Due to its unclear taxonomic classification status, the conservation and utilization of this germplasm resource have been limited. In this study, we analyzed the chloroplast genomes and nuclear sequences to reveal the taxonomic relationships among C. bretschneideri and related species. We assembled the chloroplast genomes of C. bretschneider and related species and varieties, including C. maximowiczii C. K. Schneid., C. maximowiczii var. ninganensis S. Q. Nie & B. J. Jen., C. pinnatifida Bunge, and C. pinnatifida var. major N. E. Br. The lengths of the chloroplast genomes ranged from 159,644 bp (C. bretschneideri) to 159,947 bp (C. pinnatifida var. major). The five Crataegus chloroplast genomes had similar features and possessed 86 to 88 protein-coding genes, 37 tRNA genes, and eight rRNA genes which were arranged in the same order. Eight mutation hotspot regions, including matk, psaB, accD, petA, clpP, trnD-GUC, psbH-petB, and trnN-GUU-trnR-ACG could be used as potential molecular markers for further studies of Crataegus genetic diversity. Phylogenetic analyses based on 17 chloroplast genomes of Crataegus and Amelanchier indicated that C. bretschneideri was related to C. maximowiczii and C. maximowiczii var. ninganensis. However, the phylogenetic trees constructed by nuclear sequences of 36 Crataegus accessions reflected a closer relationship between C. bretschneideri and C. pinnatifida. Furthermore, divergence time estimation suggested that C. bretschneideri and C. maximowiczii diverged in the late Miocene and that speciation of C. pinnatifida occurred during the middle to late Miocene. These findings revealed that C. bretschneideri is an independent species and may be of hybrid origin.
... It has long been difficult to classify the genera of the Maleae tribe, which may be due to polyploidy events, rapid radiations, frequent hybridizations, and/or ancient diversification among some clades (Wolfe and Wehr, 1988;Robertson et al., 1991;Vamosi and Dickinson, 2006;Campbell et al., 2007;Dickinson et al., 2007;Li et al., 2012;Lo and Donoghue, 2012;Xiang et al., 2016;Liu et al., 2019). The latest research also shows that multiple ancient hybridization and chloroplast capture events within Eriobotrya in the Yunnan-Guizhou Plateau (Chen et al., 2021). ...
Eriobotrya (Rosaceae) is an economically important genus with around 30 species. It is widely distributed in tropical and warm temperate regions of Asia, with most of its species in China, Myanmar, and Vietnam. However, Eriobotrya is often confused with the smaller genus Rhaphiolepis, and the phylogenetic relationships between the two genera are controversial. Here we present phylogenetic analyses of 38 newly generated Eriobotrya and Rhaphiolepis nrDNA together with 16 sequences of nrDNA and 28 sequences of ITS obtained from GenBank, representing 28 species of Eriobotrya and 12 species of Rhaphiolepis, in order to reconstruct highly supported relationships for the two genera. Contrary to previous research based on limited sampling, our results highlight the monophyly of Eriobotrya as well as Rhaphiolepis. The topology recovered here is consistent with key morphological synapomorphies such as the persistent sepals in Eriobotrya. Our findings show that increased sampling of taxa can provide a more robust phylogeny through reducing phylogenetic error and increasing overall phylogenetic accuracy.
... Due to the geologic and climatic oscillations, the once more widely distributed flora was fragmented and became relict in four major refugia: East Asia, eastern North America, western North America, and Mediterranean Europe/West Asia. Based on phylogenetic analyses of 47 chloroplast genomes, Nikiforova et al. (2013) suggested a North American origin of Malus, which was in accordance with the fossil evidence, because many fossils were recorded in the middle to late Eocene from western North America (Wolfe and Wehr, 1988;Manchester, 1994;Wehr and Hopkins, 1994;Axelrod, 1998;Leopold and Clay-Poole, 2001;Wheeler and Manchester, 2002;Campbell et al., 2007). Contrasting this New World origin hypothesis, Jin (2014) proposed an alternative hypothesis of East Asian origin based on biogeographic analyses using complete plastome data. ...
Phylogenomic evidence from an increasing number of studies has demonstrated that different data sets and analytical approaches often reconstruct strongly supported but conflicting relationships. In this study, 785 single‐copy nuclear genes and 75 complete plastomes were used to infer the phylogenetic relationships and estimate the historical biogeography of the apple genus Malus sensu lato, an economically important lineage disjunctly distributed in the Northern Hemisphere and involved in known and suspected hybridization and allopolyploidy events. The nuclear phylogeny recovered the monophyly of Malus s.l. (including Docynia); however, the genus was supported to be biphyletic in the plastid phylogeny. An ancient chloroplast capture event in the Eocene in western North America best explains the cytonuclear discordance. Our conflict analysis demonstrated that ILS, hybridization, and allopolyploidy could explain the widespread nuclear gene tree discordance. One deep hybridization event (Malus doumeri) and one recent event (Malus coronaria) were detected in Malus s.l. Furthermore, our historical biogeographic analysis integrating living and fossil data supported a widespread East Asian‐western North American origin of Malus s.l. in the Eocene, followed by several extinction and dispersal events in the Northern Hemisphere. We also propose a general workflow for assessing phylogenomic discordance and biogeographic analysis using deep genome skimming data sets.
... The generic delimitation in Maleae has been notoriously difficult, which may be due to the low sequence divergence resulted from ancient, rapid radiations (Wolfe and Wehr, 1988;Campbell et al., 2007) and/or frequent hybridizations Lo and Donoghue, 2012;Liu et al., 2019). As the one of the few genera of Maleae largely distributed in subtropical and tropical regions , Eriobotrya consists of ca. ...
The Eriobotrya-Rhaphiolepis (ER) clade consists of about 46 species distributed in East and Southeast Asia. Although Eriobotrya and Rhaphiolepis have been supported to form a clade, the monophyly of Eriobotrya and Rhaphiolepis at the genus level has never been well tested and their phylogenetic positions in Maleae still remain uncertain. This study aims to reconstruct a robust phylogeny of the ER clade in the framework of Maleae with a broad taxon sampling and clarify the phylogenetic relationship between Eriobotrya and Rhaphiolepis. This study employed sequences of the whole plastome (WP) and entire nuclear ribosomal DNA (nrDNA) repeats assembled from the genome skimming approach and included 83 samples representing 76 species in 32 genera of Rosaceae, especially Maleae. The Maximum Likelihood (ML) and Bayesian Analysis (BI) based on three datasets, i.e., WP, coding sequences of plastome (CDS), and nrDNA, strongly supported the paraphyly of Eriobotrya, within which Rhaphiolepis was nested. Our plastid tree supported the sister relationship between the ER clade and Heteromeles, and the nrDNA tree, however, did not resolve the phylogenetic placement of the ER clade in Maleae. Strong incongruence between the plastid and the nuclear trees is most likely explained by hybridization events, which may have played an important role in the evolutionary history of the ER clade. Molecular, morphological, and geographic evidence all supports the merge of Eriobotrya with Rhaphiolepis, which has the nomenclatural priority. We herein transferred 36 taxa of Eriobotrya to Rhaphiolepis. We also proposed a new name, Rhaphiolepis loquata B.B.Liu & J.Wen, for the economically important loquat, as the specific epithet “japonica” was pre-occupied in Rhaphiolepis.
... Diverse record of fossil endocarps and leaves of Prunus s. l. is available for Eocene of North America, Europe and Asia (e.g., Cevallos-Ferriz and Stockey 1991;Cevallos-Ferriz et al. 1993;DeVore and Pigg 2010;Li et al. 2011;Mai 1984;Manchester 1994;Wolfe and Wehr 1988). Permineralized seeds and wood fragments related to Prunus are known from the latest Early to earliest Middle Eocene Princeton chert of British Columbia, Canada (Cevallos-Ferriz 1989;Cevallos-Ferriz andStockey 1990, 1991;Pigg and DeVore 2016), and fossil wood comparable to Prunus s. l. is found in the late Eocene of Nebraska (Wheeler and Landon 1992) and in the Eocene of Yellowstone National Park (Wheeler et al. 1978). ...
The late Eocene ambers provide plethora of animal and plant fossils including well-preserved angiosperm flowers from the Baltic amber. The Rovno amber from NW Ukraine resembles in many aspects the Baltic amber; however, only fossilized animals and some bryophytes have yet been studied from the Rovno amber. We provide the first detailed description of an angiosperm flower from Rovno amber. The flower is staminate with conspicuous hypanthium, double pentamerous perianth and whorled androecium of 24 stamens much longer than the petals. Sepals are sparsely pubescent and petals are densely hirsute outside. The fossil shares important features with extant members of Prunus subgen. Padus s. l. (incl. Laurocerasus, Pygeum and Maddenia), especially with its evergreen paleotropical species. It is described here as a new species Prunus hirsutipetala D.D.Sokoloff, Remizowa et Nuraliev. Our study provides the first convincing record of fossil flowers of Rosaceae from Eocene of Europe and the earliest fossil flower of Prunus outside North America. Our record of a plant resembling extant tropical species supports palaeoentomological evidences for warm winters in northwestern Ukraine during the late Eocene, as well as suggesting a more significant role of tropical insects in Rovno amber than inferred from Baltic amber.
... So in the Eocene floras, most species can be classified within contemporary families. So, it is quite natural that certain fossilized footprints of Amelanchier are found in western North America, namely in the deposits of the Eocene period (48-50 million years ago) [58]. During the Neogene, in the arid regions of North America, a kind of "Madro-Tertiary" flora was formed, a detailed study of which [59] showed genus Amelanchier among other typical representatives of the fossil flora. ...
Opalko, A. I., Andrienko, O. D., & Opalko, O. А. (2016). Phylogenetic connections between representatives of the genus Amelanchier Medik. Temperate crop science and breeding. Ecological and genetic studies [Eds.: Sarra A. Bekuzarova, Nina A. Bome, Anatoly I. Opalko et al.]. Boca Raton; Oakville: Apple Academic Press. Part 2. Horticultural Crop Science. Ch. 11. P. 201–232.
ABSTRACT
Within the frames of retrospective discourse, the information concerning breeding value of a representative of the genus Amelanchier Medik. — for national pomiculture, decorative gardening, and pharmacy — is integrated. This article characterizes their: biological peculiarities, ecological adaptiveness, palatability traits and cooking qualities of their fruits, their availability for drying and processing, namely preparing juices, syrups, jams, candied fruit jellies, comfiture, and also fruit wine. The effectiveness of using Juneberry for phytomeliorative is mentioned, some ethnobotanical aspects are discussed. Data about chromosome numbers and the geographical origin of the genus Amelanchier representatives cultivated in Ukraine and their closest congeners from the family Rosaceae Juss. are cited. Controversial questions of the genus Amelanchier system were discussed from the classical and molecular genetic approaches. The results of phylogenetical and molecular genetic researches made by scientists of different countries offer a possibility to specify the systematic position of the genus Amelanchier representatives of the family Rosaceae Juss. grown in Ukraine, and to place them temporarily in a big subfamily Amygdaloideae Arn., which combines the former subfamilies Amygdaloideae, Spiraeoideae, and Maloideae, tribe—Maleae Small, subtribe – Malinae Rev.
... These studies also support the theory that the subtribe is of American origin as Gillenia, Vauquelinia and Lindleya are only found in the New World. Fossil records indicate speciation commenced approximately 50 million years ago, almost 80 million years after formation of the Atlantic rift (Wolfe and Wehr, 1988). ...
Aronia (Medik.), commonly known as chokeberry, is a taxonomically misunderstood genus currently experiencing a renaissance in North America as both an ornamental and fruit crop. Three species of chokeberry are commonly accepted as native in North America: A. arbutifolia (L.) Pers. red chokeberry; A. melanocarpa (Michx.) Elliot, black chokeberry; and A. prunifolia (Marshall) Rehder, or purple chokeberry. In Europe a fourth species of human origin is recognized as Aronia mitschurinii (A.K.Skvortsov & Maitul.), or cultivated, black-fruited Aronia. It is widely speculated that this genotype originated in the early 20th century with Russian pomologist Ivan Michurin, as the product of his experiments in wide hybridizations. In my research I attempt to determine the feasibility of this hypothesis by exploring Aronia’s crossing capabilities and testing the relationships of A. mitschurinii to wild Aronia species and several other Pyrinae genera using amplified fragment length polymorphic (AFLP) analysis. Successful seed formation was achieved between maternal diploid A. melanocarpa and Malus domestica, Photinia serrulata, Sorbus, and ×Sorbaronia. Clustering of AFLP similarity data using the unweighted pair group method with arithmetic mean (UPGMA) identified A. mitschurinii as distinct from wild Aronia spp., placing it on a branch with ×Sorbaronia fallax and ×Sorbaronia ‘Ivan’s Beauty’. Non-metric multidimensional scaling (nMDS) clustered A. mitschurinii apart from wild Aronia spp., and demonstrated a relationship between Sorbus aucuparia, ×Sorbaronia fallax, and Aronia. Bayesian analysis revealed A. mitschurinii to possess genetic influence from the genus Sorbus subgenus Sorbus.
... So in the Eocene floras, most species can be classified within contemporary families. So, it is quite natural that certain fossilized footprints of Amelanchier are found in western North America, namely in the deposits of the Eocene period (48-50 million years ago) [69]. During the Neogene, in the arid regions of North America, a kind of "Madro-Tertiary" flora was formed, a detailed study of which [7] showed genus Amelanchier among other typical representatives of the fossil flora. ...
The information on fruit and decorative value, honey and medicinal properties of the genus Amelanchier Medik. is generalized. Their biological characteristics, chemical composition and palatability traits of the fruit, the ways of consumption and processing, including drying, preparing juices, syrups, jams, candied fruit jellies, confiture, and fruit wine are specified. The environmental adaptability and effectiveness of using juneberry for phytomelioration are mentioned. Several versions of the origin of the genus Amelanchier name and interpretation of its specific epithets are described. The controversial issues of the genus Amelanchier system were discussed from the classical and molecular genetic approaches. The attention is focused on two main aspects of views on the place of the genus Amelanchier representatives of the family Rosaceae Juss. within the particular subfamily, namely the subfamily Pyroideae Burnett (Maloideae S. Weber) or the subfamily Amygdaloideae Arn., which indicates the necessity for further comparative morphological and molecular genetic studies of the family Rosaceae. The directions of evolution, habitat and invasive ability of some species of the genus Amelanchier are characterised. The list of the genus Amelanchier representatives cultivated in Ukraine is given.
... Therefore, evolution of the two GBSS gene pairs, MdGBSSII-1/MdGBSSII-3 and MdGBSSII-2/ MdGBSSII-5, is likely attributed to two WGD events. This finding suggests that the second WGD event must have occurred very recently, ,18 MYA, and later than the archeobotanical dates of 48 to 50 MYA [35]. This observed difference may be attributed to the fact that our estimation is based on segmental duplication rather than WGD of the apple genome. ...
Starch is one of the major components of cereals and many fruits. Granule-bound starch synthase (GBSS) genes, responsible for amylose synthesis, have been used to study phylogenetic and evolutionary relationships in many plant species due to their low copy number. In this study, sequences of GBSS genes isolated from three fruit trees, including apple, peach, and orange, together with an additional 22 GBSS sequences from various monocots and eudicots, available in public databases, were used to investigate a comprehensive evolutionary history of the GBSS gene across monocots and eudicots. It is revealed that the structure of GBSS genes in monocots and eudicots is conserved and all sequences must have evolved from a common ancestor. Moreover, the GBSS gene in the ancestral angiosperm must have undergone a duplication event approximately 251 million years ago (MYA) to generate two families: GBSSI and GBSSII. Both GBSSI and GBSSII are present in monocots; whereas, GBSSI is absent in eudicots. Thus, a major divergence event in the ancestral GBSSII, ~165 MYA when monocots and dicots split, has given rise to monocot-specific GBSSII and eudicot GBSS genes. In eudicots, multiple GBSS genes within the same species have high levels of sequence divergence although they have higher identity among each other than with either GBSSI or GBSSII genes from monocots. Overall these findings suggest that GBSSII of monocots must have an orthologous relationship with GBSS genes of eudicots. As in monocots, GBSSI and GBSSII are expressed in both storage and non-storage tissues, respectively, and they may be associated with neofunctionalization of starch synthase.
... Тільки з аридізацією внутрішньої частини Північної Америки там розпочалося підсилене видоутворення Crataegus (Криштофович, 1957). Найдавніші відбитки листків та викопні рештки плодів Crataegus належать кінцю олігоцену (MacGinitie, 1933;Oliver, 1934;Hickey, 1984;Wolfe, Wehr, 1988;DeVore, Pigg, 2007). Олігоценовий північноамериканський C. newberty близький до сучасного азійського C. pinnatifida (Lakhanpal, 1958). ...
The results of the investigation of hawthorn species introduced by authors in Artemivsk Experimental Station of Nursery Cultivation have been given, and works on Crataegus in Ukraine have been reviewed. Genus Crataegus system has been considered, a new combination C. submollis var. arnoldiana has been proposed. Eco-biological characterization of hawthorn species under condition South-East of Ukraine has been given. Species and cultivars promising for growing as ornamental, fruit and medicinal plants have been described.
... Betula leopoldae Wolfe & Wehr (Crane and Stockey 1986;Wolfe and Wehr 1987) and Palaeocarpinus stonebergae Pigg, Manchester & Wehr (Pigg et al. 2003) represent Betulaceae. Two plants from Rosaceae, Stonebergia columbiana Wolfe & Wehr, an extinct genus (Wolfe and Wehr 1988), and Neviusia dunthornei DeVore, Moore, Pigg & Wehr, are known (DeVore et al. 2004). Modern Neviusia has a disjunct distribution with one species from southeastern North America and the other from northern California, which the fossil species resembles more closely. ...
A flora from Thomas Ranch near Princeton, British Columbia, Canada, is assessed for biodiversity and paleoclimate. This latest Early to early Middle Eocene flora occurs in the Allenby Formation. Seventy-six megafossil morphotypes have been recognized, representing at least 62 species, with 29 identified to genus or species. Common taxa include Ginkgo L., Metasequoia Miki, Sequoia Endl., Abies Mill., Pinus L., Pseudolarix Gordon, Acer L., Alnus Mill., Betula L., Fagus L., Sassafras J Presl, Macginitiea Wolfe & Wehr, Prunus L., and Ulmus L. More than 70 pollen and spore types are recognized, 32 of which are assignable to family or genus. The microflora is dominated by conifers (85%–97% abundance), with Betulaceae accounting for most of the angiosperms. The Climate Leaf Analysis Multivariate Program (CLAMP) calculates a mean annual temperature (MAT) of 9.0 ± 1.7 °C and bioclimatic analysis (BA) calculates a MAT of 12.8 ± 2.5 °C. Coldest month mean temperature (CMMT) was >0 °C. Mean annual precipitation (MAP) was >70 cm/year but is estimated with high uncertainty. Both the CLAMP and BA estimates are at the low end of the MAT range previously published for other Okanagan Highland localities, indicating a temperate climate consistent with a mixed conifer–deciduous forest.
... Tel111inology should not stand in the way of this. WOLFE and WEHR (1988) differentiate living simple and compound leaves on the basis of the degree to which discrete units of the leaf are de ciduous. According to their usage, in simple leaves only the leaf dehisces while in compound leaves discrete laminar units dehisce. ...
Fossil legume fruits and leaflets from two localities in the Middle Eocene Claiborne Formation from western Tennessee are described and assigned to the extant pantropical genus Crudia (Caesalpinioideae, Detarieae). Morphological and anatomical features of the fruits and leaflets are used in evaluating the systematic relationships of these fossils. The fossils are more similar to several Crudia species from tropical America and Africa than they are to the species studied from Asia. These fossils represent the only documented occurrence of Crudia megafossils and confirm its existence by the Middle Eocene.
... Rosaceous remains from the early Middle Eocene assemblages of Canada and the Pacific Northwest, U.S.A., include 40 taxa based on leaf impressions and compressions (WOLFE and WEHR 1988). In the roughly correlative Princeton chert one taxon based on twigs, branches, and mature wood (CEvALLos-FERRIz and STOCKEY 1990b), and the flowers of Paleorosa (BASINGER 1976; ...
Three anatomically preserved endocarps, each with one enclosed seed, are described from the Princeton chert (Middle Eocene) Allenby Formation of British Columbia, Canada. Fruits are ovoid, unicarpellate, single-seeded drupes. Endocarps are sclerotic, with one or two ridges on the dorsal side, and a distinct ventral suture that is partially open toward the fruit apex where an obturator is present. Cells along the ventral suture are oriented parallel to the surface of the suture and have thin secondary walls and dark contents. Seeds are anatropous, bitegmic, and ventrally attached to the carpel, with a ventral raphe and a dorsal vascular plexus. The outer integument in two seeds is composed of a single layer with alternating sclereids and thin-walled cells, while in the third seed only sclereids are present. The inner integument consists of a single layer of rectangular, thin-walled cells, but the inner integument becomes multilayered in the micropylar region and along the vascular plexus. These three endocarps with enclosed seeds have a very similar anatomy. Variation in number of cell layers, and cell size and shape in each zone is similar to that seen in extant Prunus species. However, only seven out of about 430 species of Prunus have been studied in detail. This lack of information in extant Prunus makes the recognition of species difficult at this time. The description of these rosaceous fruits shows that by the Middle Eocene several postulated "advanced" characters in Prunoideae were already present.
... Pollen assigned to Malus or Pyrus has been reported from the late Eocene Florissant locality in Colorado (Leopold and Clay-Poole 2001) estimated to be of 34.07 ± 0.10 Ma age. Fossils with similarity to Amelanchier, Crataegus, and Photinia, as well as some relatives of Malus and Sorbus, are known from the early middle Eocene (48-50 Ma) (Campbell et al. 2007; Wolfe and Wehr 1988). ...
Both the origin of domesticated apple and the overall phylogeny of the genus Malus are still not completely resolved. Having this as a target, we built a 134,553 position long alignment including two previously published cpDNAs and 45 de novo sequenced, fully co-linear chloroplast genomes from cultivated apple varieties and wild apple species. The data produced are free from compositional heterogeneity and from substitutional saturation, which can adversely affect phylogeny reconstruction. Phylogenetic analyses based on this alignment recovered a branch, having the maximum bootstrap support, subtending a large group of the cultivated apple sorts together with all analyzed European wild apple (Malus sylvestris) accessions. One apple cultivar was embedded in a monophylum comprising wild M. sieversii accessions and other Asian apple species. The data demonstrate that M. sylvestris has contributed chloroplast genome to a substantial fraction of domesticated apple varieties, supporting the conclusion that different wild species should have contributed the organelle and nuclear genomes to domesticated apple.
... Therefore, evolution of the two GBSS gene pairs, MdGBSSII-1/MdGBSSII-3 and MdGBSSII-2/ MdGBSSII-5, is likely attributed to two WGD events. This finding suggests that the second WGD event must have occurred very recently, ,18 MYA, and later than the archeobotanical dates of 48 to 50 MYA [35]. This observed difference may be attributed to the fact that our estimation is based on segmental duplication rather than WGD of the apple genome. ...
Starch is one of the major components of cereals, tubers, and fruits. Genes encoding granule-bound starch synthase (GBSS), which is responsible for amylose synthesis, have been extensively studied in cereals but little is known about them in fruits. Due to their low copy gene number, GBSS genes have been used to study plant phylogenetic and evolutionary relationships. In this study, GBSS genes have been isolated and characterized in three fruit trees, including apple, peach, and orange. Moreover, a comprehensive evolutionary study of GBSS genes has also been conducted between both monocots and eudicots. Results have revealed that genomic structures of GBSS genes in plants are conserved, suggesting they all have evolved from a common ancestor. In addition, the GBSS gene in an ancestral angiosperm must have undergone genome duplication ∼251 million years ago (MYA) to generate two families, GBSSI and GBSSII. Both GBSSI and GBSSII are found in monocots; however, GBSSI is absent in eudicots. The ancestral GBSSII must have undergone further divergence when monocots and eudicots split ∼165 MYA. This is consistent with expression profiles of GBSS genes, wherein these profiles are more similar to those of GBSSII in eudicots than to those of GBSSI genes in monocots. In dicots, GBSSII must have undergone further divergence when rosids and asterids split from each other ∼126 MYA. Taken together, these findings suggest that it is GBSSII rather than GBSSI of monocots that have orthologous relationships with GBSS genes of eudicots. Moreover, diversification of GBSS genes is mainly associated with genome-wide duplication events throughout the evolutionary course of history of monocots and eudicots.
... Alignability of maloid GBSSI introns is straightforward, many maloid genera may be grafted successfully, there are numerous natural intergeneric hybrids , and sequence divergence is low in four cpDNA genes: matK (C. S. Campbell, unpublished data), ndhF (Evans, 1999), rbcL (Morgan, Soltis, and Robertson, 1994), and trnL (C. S. Campbell, unpublished data). This lack of divergence is surprising in a group that extends back to at least the Middle Eocene (Wolfe and Wehr, 1988). This limited evolutionary divergence could be a result of relatively slow rates of evolution in woody plants or of continued gene flow between the genera or a combination of these two factors. ...
For 70 yr the leading hypothesis for the origin of the Maloideae has involved wide hybridization between ancestors of two other subfamilies. The basis of this hypothesis is that Maloideae have a base chromosome number of 17, whereas other Rosaceae are mostly x = 7, 8, or 9. To investigate this hypothesis we cloned and sequenced approximately 1.8 kilobases from the 5' portion of granule-bound starch synthase (GBSSI, or waxy) genes for 89 clones from 32 Rosaceae genera. Previous studies demonstrate the presence of two copies in all Rosaceae (GBSSI-1 and GBSSI-2) and four in Maloideae (GBSSI-1A, GBSSI-1B, GBSSI-2A, and GBSSI-2B). Parsimony and maximum likelihood analyses nest Gillenia, a genus of the southeastern United States with a base chromosome number of 9, within either Maloideae GBSSI-1 or GBSSI-2. Monophyly of Maloideae plus Gillenia is well supported by bootstrap values, loss of the sixth intron in all GBSSI-1 sequences, intron alignability between genera, and numerous nonmolecular characters. Our results falsify the wide-hybridization hypothesis and are consistent with a polyploid origin involving only members of a lineage that contained the ancestors of Gillenia. Under this hypothesis, the subfamily originated in North America, and the high Maloideae chromosome number arose via aneuploidy from x = 18.
... Molecular markers linked to a number of agronomically important traits, such as resistance to pests and diseases, tree architecture, and fruit quality, have been identified in both apple [3] and pear [4]. Their identical chromosome number (2n = 2x = 34) and similar genome size (apple 1.57 pg/2C [5]; pear 1.11 pg/ 2C) [6], as well as their supposed recent divergence date (33.9 to 55.8 million years ago [7]) suggests that their genomes might be highly co-linear. When co-linearity between Malus and Pyrus was examined by comparing maps of the European pears (Pyrus communis) 'Bartlett' and 'La France', and the Japanese pear (Pyrus pyrifolia) 'Housui' with those of apple cultivars (Malus × domestica) 'Fiesta' and 'Discovery' [8] using 66 transferable apple simple sequence repeat (SSR) loci, all the pear linkage groups were aligned to the apple consensus linkage groups with at least one marker in common [9]. ...
Comparative genome mapping determines the linkage between homologous genes of related taxa. It has already been used in plants to characterize agronomically important genes in lesser studied species, using information from better studied species. In the Maloideae sub-family, which includes fruit species such as apple, pear, loquat and quince, genome co-linearity has been suggested between the genera Malus and Pyrus; however map comparisons are incomplete to date.
Genetic maps for the apple rootstocks 'Malling 9' ('M.9') (Malus x domestica) and 'Robusta 5' ('R5') (Malus x robusta), and pear cultivars 'Bartlett' and 'La France' (Pyrus communis) were constructed using Simple Sequence Repeat (SSR) markers developed from both species, including a new set of 73 pear Expressed Sequence Tag (EST) SSR markers. Integrated genetic maps for apple and pear were then constructed using 87 and 131 SSR markers in common, respectively.The genetic maps were aligned using 102 markers in common, including 64 pear SSR markers and 38 apple SSR markers. Of these 102 markers, 90 anchor markers showed complete co-linearity between the two genomes.
Our alignment of the genetic maps of two Malus cultivars of differing species origin with two Pyrus communis cultivars confirms the ready transferability of SSR markers from one genus to the other and supports a high level of co-linearity within the sub-family Maloideae between the genomes of Malus and Pyrus.
About forty species, including a bryophyte, ferns, conifers, Ginkgo, and over 35 angiosperms, are recognized based on compression-impression remains from the early Eocene of Horsefly, British Colombia, Canada. This flora is in the north central part of a chain of late early Eocene fossil assemblages known as floras of the “Okanagan Highlands” (= “Okanogan Highlands” in the US). These floras extend from north central British Columbia, Canada southeast to Republic, Washington, USA. The Horsefly flora shows similarities to other Eocene Okanagan Highlands floras, such as McAbee, Falkland, Thomas Ranch and Republic, but with some additional rare taxa. In the broader sense, the Horsefly flora can be compared with early and middle Eocene floras of eastern Asia and midcontinental North America, but shares fewer elements with Europe. Ginkgo, Metasequoia, Pinus, Palaeocarpinus, ulmaceous leaves and Deviacer are shared with northeastern China as well as western North American sites. Fagopsis, Macginitiea, Dipteronia, Florissantia, Sassafras and Lagokarpos also occur in other western North American Eocene floras and Koelreuteria and Jenkinsella with Eocene paleofloras of China. These comparisons demonstrate probable floristic exchange between northwestern North America and northeastern China via a Beringian route during the late early Eocene.
In lineages of allopolyploid origin, sets of homoeologous chromosomes may coexist that differ in gene content and syntenic structure. Presence or absence of genes and microsynteny along chromosomal blocks can serve to differentiate subgenomes and to infer phylogenies. We here apply genome-structural data to infer relationships in an ancient allopolyploid lineage, the walnut family (Juglandaceae), by using seven chromosome-level genomes, two of them newly assembled. Microsynteny and gene-content analyses yield identical topologies that place Platycarya with Engelhardia as did a 1980s morphological-cladistic study. DNA-alignment-based topologies here and in numerous earlier studies instead group Platycarya with Carya and Juglans, perhaps misled by past hybridization. All available data support a hybrid origin of Juglandaceae from extinct or unsampled progenitors nested within, or sister to, Myricaceae. Rhoiptelea chiliantha, sister to all other Juglandaceae, contains proportionally more DNA repair genes and appears to evolve at a rate 2.6- to 3.5-times slower than the remaining species.
Global climate changes during the Miocene may have created ample opportunities for hybridization between members of tropical and subtropical biomes at the boundary between these zones. Yet, very few studies have explored this possibility. The Yunnan-Guizhou Plateau (YGP) in Southwest China is a biodiversity hotspot for vascular plants, located in a transitional area between the floristic regions of tropical Southeast Asia and subtropical East Asia. The genus Eriobotrya (Rosaceae) comprises both tropical and subtropical taxa, with 12 species recorded in the YGP, making it a suitable basis for testing the hypothesis of between-biome hybridization. Therefore, we surveyed the evolutionary history of Eriobotrya by examining three chloroplast regions and five nuclear genes for 817 individuals (47 populations) of 23 Eriobotrya species (including 19 populations of 12 species in the YGP), plus genome re-sequencing of 33 representative samples. We concluded that: 1) phylogenetic positions for 16 species exhibited strong cyto-nuclear conflicts, most likely due to ancient hybridization; 2) the YGP is a hotspot for hybridization, with 11 species showing clear evidence of chloroplast capture; and 3) Eriobotrya likely originated in tropical Asia during the Eocene. From the Miocene onwards, the intensification of the Eastern Asia monsoon and global cooling may have shifted the tropical-subtropical boundary and caused secondary contact between species, thus providing ample opportunity for hybridization and diversification of Eriobotrya, especially in the YGP. Our study highlights the significant role that paleo-climate changes likely played in driving hybridization and generating rich species diversity in climate transition zones.
Blue tomatoes, pink bananas and red-fleshed apples. Meet the next generation of healthy fruits.
CLAMP (Climate-Leaf Analysis Multivariate Program) uses Correspondence Analysis of 29 rigorously defined character states of foliar physiognomy to order leaf samples. The database of modern vegetation comprises 106 samples, each composed of >19 species of woody dicotyledons collected proximal to a meteorological station. The two principal axes in Correspondence Analysis account for ~70 % of physiognomic variation. Ordination of the samples on Axis I reflects various temperature parameters and on Axis II various water-stress parameters. Regression analysis of relative placement of the samples indicates that mean annual temperature (MAT) and cold-month mean temperature (CMMT) can be estimated with a standard error of <1° and <2 °C, respectively. Analyses of water-stress factors tend to produce only general estimates of, for example, seasonal drought and growing season precipitation; certain critical levels are emphasized by these analyses. Any fossil leaf sample of woody dicotyledons can be analysed in the CLAMP database and various palaeoclimatic parameters estimated.
The sequence of leaf assemblages on the Yakutat block, which is now at lat. 60° N at the head of the Gulf of Alaska, was, during the Eocene, located as the coastal fringe of southeastern Alaska. During the Eocene, however, the Yakutat assemblages represent vegetation at 65–70 °N, because of the subsequent counterclockwise rotation of North America. The composite Kulthieth assemblages represents the Early Eocene thermal maximum; CLAMP analyses indicate a MAT of 19.4°C and a CMMT >12 °C. Marginal Paratropical Rain forest thus extended along the coast of western North America to ~70 °N. CLAMP analyses of the Middle Eocene (~45 Ma) and latest Eocene (~34 Ma) Yakutat assemblages produce MAT estimates of ~17 °C and 16 °C, respectively, suggesting overall cooling during the Eocene. At the same time, CMMT also decreased, and climates became more extreme, although not as extreme as after ~33 Ma.
Terranes of the main part of southern Alaska were accreted to cratonic Alaska by the end of the Mesozoic. The Chickaloon assemblage has latest Palaeocene radiometric ages, and palaeomagnetic analysis of volcanic flows elsewhere on the same terrane indicates that the Chickaloon represents vegetation at ~75 °N. CLAMP analyses indicate that the Chickaloon represents microthermal mixed broad-leaved evergreen and coniferous forest. This modern vegetation type has many arcto-tertiary clades, but the Chickaloon flora is dominated by deciduous Taxodiaceae and extinct lineages of clades such as Trochodendrales and Hamamelidales. Significant numbers of extant arcto-tertiary lineages appear in Alaska ~5 Ma after their first appearance at high altitudes in middle latitudes.
Woody or herbaceous. Leaves usually alternate, sometimes distichous, rarely opposite, simple or compound; stipules on the twig or on the base of the petiole, free or adnate to the petiole, rarely O. Inflorescences various, usually terminal, usually (compound) racemes. Flowers actinomorphic, mostly (4)5-merous, mostly bisexual, rarely unisexual and then the plants monoecious or dioecious; hypanthium usually well-developed (not evident in some staminate flowers), from saucer-shaped to tubular or camp anulate, the epicalyx, sepals, petals, and stamens inserted on its rim, its inside usually lined by nectariferous tissue; disk sometimes distinct, intrastaminal; epicalyx + in some genera; sepals free; petals free, from large and showy to small and not or hardly distinct from sepals, rarely 0; stamens few to numerous, often their number distinctly related to the number of perianth parts; filaments free; anthers bilocular, dehiscing longitudinally; carpels 1-many, free or variously connate with each other and/or adnate to the hypanthium, forming 1 or more superior to inferior ovary(ies); stylodia (in monocarpellate ovaries styles) +, these sometimes (some Maleae) fused into a common, branched style; ovules 1-several (often 2) per carpel, anatropous, ascending or pendulous. Fruits various, fleshy or dry, dehiscent or not; seeds 1-several, testa usually firm, endosperm 0 or a thin layer, cotyledons fleshy or flat.
Application of multivariate statistical techniques, especially correspondence analysis, results in the recognition of four major communities for the Creede plant assemblages: fir-spruce forest, fir-pine forest, pine-juniper forest or woodland, and mountain mahogany chaparral. Physiognomy of the Creede assemblages indicates a mean annual temperature of <2.5°C. A variety of data indicate that summers were dry and most precipitation occurred as snow. The stratigraphic sequence of assemblages indicates that significant precipitational change occurred during deposition of the Creede plant-bearing beds. Consideration of the adaptive and morphologic histories of the Creede lineages suggests that physiologic adaptation may precede morphologic change. The Creede forest communities have no modern homologues. -from Authors
Genome resources for apple (Malus × domestica Borkh), the main fruit crop of temperate regions, have been developed over the past 10 years, culminating in the sequencing of the ‘Golden Delicious’ genome. The apple genome sequence anchored to a high-density linkage map provides the apple community with new tools to identify genes and other functional elements that will enable the study of the evolution of plant genome structure, as well as facilitating genomic-assisted breeding. Transcriptomics, proteomics and metabolomics studies are greatly benefiting from the availability of an annotated genome. In this review, we report on the status of the apple genome and on current molecular and genetic tools available in apple that will improve the efficiency of the process of cultivar development; we discuss how an integrative ‘omics’ approach could greatly enhance the understanding of biological processes that determine agronomically and economically favorable phenotypes; we review the databases and bioinformatics tools that are available to manage and exploit the large amounts of biological data generated for apple and other plant genomes.
The biogeographic affinities of the Cretaceous and early Tertiary angiosperm floras of the North American area (which includes Meso-America, and the Greater Antilles) have been the subject of considerable interest. Although recent treatments of isolated taxa have shown affinities between North American, European, east Asian and Neotropic floras, the relationships have not been quantified. This study compiles the records of fossils whose familial relationships seem secure. This provides a carefully culled, and uniformly presented review of the Cretaceous and Paleogene record from 1950 to 1989 and supplements LaMotte (1950). A subset of these records, which showed compelling evidence of subfamilial relationships, was analyzed to quantify the relationships of the Cretaceous, Paleocene, Eocene and Oligocene floras to other regions. The analysis suggests that for the entire period 24% of the fossil species had affinities with extant taxa from the Northern Hemisphere; 10% with taxa from the Northern Hemisphere that have a few species in South America; 17% with taxa from Eurasia; 3% with taxa with a disjunct Eurasian-South American pattern; 19% with taxa from South America and/or Africa; 8% with taxa from South America and/or Africa that have an important sister group in southeast Asia; 5% with taxa from the Old World; and 13% with taxa having other distribution patterns. Those fossils with affinities to Laurasian taxa are mostly found in the northern and western portions of the North American area. The fossils with affinities to South American and/or African taxa are found in the southern portions of North America, Meso-America, and the Greater Antilles. The taxa with disjunct distributions show both patterns. These patterns suggest that during this time there were wide-spread temperate elements, found throughout Laurasia; Boreotropical flora elements, distributed in North America, Europe and along the Tethys seaway to southeast Asia; and West Gondwana elements which show dispersion from South America across the proto-Caribbean. The paleobotanical data are compatible with current geological, paleontological and biogeographical studies.
Thome, Robert F. (Rancho Santa Ana Botanic Garden, Claremont, CA 91711). Classification and geography of the flowering plants. Bot. Rev.58(3): 225–348. 1992.—This treatment of the flowering plants is the latest revision of my classification of the Class Angiospermae and replaces my 1983 and more recent 1992 synopses. An update is necessary because so much new information has been published in the last decade pertinent to the classification of the flowering plants. About 870 such recent books, monographs, and other botanical papers are cited in the Introduction, listed primarily by the botanical discipline that they represent. Also considerable changes in my classification have been necessitated by my narrowed family- and ordinal-gap concepts, acceptance of the ending “-anae” for superorders in place of the traditional but inappropriate “-iflorae,” and acceptance of more prior or more widely used names for the categories above the family. A new phyletic “shrub” replaces earlier versions, and attempts to indicate visually relative sizes and relationships among the superorders, orders, and suborders. One table includes a statistical summary of floweringplant taxa: ca. 233,900 species of 12,650 genera, 437 families, and 708 subfamilies and undivided families in 28 superorders, 71 orders, and 71 suborders of Angiospermae. Three other tables summarize the known indigenous distribution of the families and subfamilies of angiosperms about the world. The synopsis lists the flowering plant taxa from the class down to the subfamily (and in Asteraceae down to the tribe) with indication of the degree of confidence I place in the circumscription and placement of each category above the subfamily, the best available estimates of the number of genera and species for each category, and the known indigenous distribution of each subfamily and family. Table V lists alphabetically the geographical abbreviations used in the synopsis. The extensive bibliography of recent literature should be helpful to those persons interested in the classification of the flowering plants.
We dedicate this issue to the memory of Wesley C. Wehr, former Affiliate Curator of Paleobotany, Burke Museum of Natural History and Culture, Seattle, Washington. Wes' contributions to paleontology, particularly in the Okanagan Highlands of Washington State and British Columbia; his influence on a generation of paleontologists (particularly paleobotanists) working in and coming from this region; and his warm friendship that brought together members of the scientific and arts communities were deeply influential, and will be fondly remembered.Nous dédions ce numéro à la mémoire de Wesley C. Wehr, ancien conservateur affilié de paléobotanique au Burke Museum of Natural History and Culture, à Seattle, Washington. La contribution de M. Wehr à la paléontologie, surtout des terres hautes de l'Okanagan en Colombie-Britannique et dans l'état de Washington, son influence sur une génération de paléontologues (surtout des paléobotanistes) provenant de ou travaillant dans cette région ainsi que son amitié chaleureuse qui rassemblait les membres des communautés scientifiques et artistiques ont eu une profonde influence et nous nous en souviendrons avec affection.
Fossil leaves assigned to the disjunct rosaceous genus Neviusia A. Gray, N. dunthornei DeVore, Moore, Pigg & Wehr sp. nov. (Rosaceae, tribe Kerrieae) are described from the lower-middle Eocene One Mile Creek locality near the town of Princeton, southern British Columbia, Canada. The leaves are elliptic to broadly ovate, seven-lobed, up to 4.9 cm long X 5.6 cm wide with craspedodromous venation and two to three sizes of marginal teeth. They bear a striking resemblance to N. cliftonii Shevock, Ertter & Taylor, the recently discovered species of the Mount Shasta area of northern California, and differ markedly from the type species N. alabamensis A. Gray of southeastern North America. The occurrence in the Okanogan Highlands of N. dunthornei marks the first fossil evidence for the small, rosaceous tribe Kerrieae, and further documents the lower-middle Eocene as a time of major radiation of many temperate families, including the Rosaceae.
Although DAVID DILCHER and JACK WOLFE were born on the same summer day (July 10, 1936) in Cedar Falls, Iowa, and Portland, Oregon, respectively, their contributions to paleobotany have been a study in contrasts. WOLFE, the architect of CLAMP, and DILCHER, who helped place angiosperin paleobotany within the context of plant systematics, have found their own innovative ways of documenting and interpreting the evolutionary history and paleoccology of the angiosperms. From the beginning, both DILCHER and WOLFE recognized that an understanding of regional geological processes was essential when determining both the kinds of questions and techniques used when studying Tertiary floras. DILCHER'S Eocene work has focused on the megathermal Claiborne Formation of the Mississippi Embayment, while WOLFE'S centered on the "upland" microthermal floras of the northwestern Okanogan Highlands. DILCHER and his students, working in the Eocene floras of the clay pits of Kentucky and Tennessee, described an extinct, dry vegetation of the Southeast that was dominated by Lauraceae, Fagaceae and Leguminosae. The exquisite preservation of these southeastern floras allowed for detailed pollen and cuticular studies that provided a high degree of taxonomic precision. In contrast, WOLFE turned his attention to floras of British Columbia and eastern Washington that are dominated temperate elements such as Betulaceae and Rosaceae in an upland environment. The ability to precisely date dramatic changes in these floras through radiometric means provided WOLFE with a database for leaf physiognomic studies and the development of CLAMP (Climate Leaf Analysis Multivariate Program). The contrasting contributions of DILCHER and WOLFE have played a significant role in the development of Tertiary North American paleobotany and its contribution to the understanding of fossil and extant floras. © E. Schweizerbart'sche Verlagsbuchhandlung (Nägele u. Obermiller), 2007.
The diverse Early to Middle Eocene Okanagan Highlands floras of south central British Columbia and northeastern Washington reflect a time of rapid evolution and the early radiation of many dicot families that are currently significant elements of temperate floras. Recent studies of the Republic, Washington flora (Klondike Mountain Formation) and related Okanagan floras in British Columbia have documented both the earliest, and sometimes the only, known fossil occurrences of genera. Today many once more widespread taxa are restricted, particularly to Asian and (or) eastern North American refugia. Examples include members of the families Betulaceae (birch, hazelnut), Rosaceae (rose), Hamamelidaceae (witch hazel), and the endemic Asian family Trochodendraceae. Earliest occurrences are noted for Neviusia (Rosaceae), Trochodendron (Trochodendraceae), Corylus and Carpinus (both Betulaceae). The first unequivocal leaf records of Corylopsis and Fothergilla (both Hamamelidaceae), and two new Eocene species of the extinct fruit Palaeocarpinus (Betulaceae) are also recognized. Today, Trochodendron and Corylopsis are restricted to Asia, whereas Neviusia and Fothergilla, genera with close Asian relatives, occur only in North America. Corylus johnsonii from Republic is most similar to the extant Asian species C. heterophylla, C. wangii, and C. ferox. Neviusia leaves from One Mile Creek near Princeton, British Columbia are more similar to N. cliftonii, an endemic from Mount Shasta, California, than to N. alabamensis of southeastern North America. A better documentation of the Okanagan Highlands floras is essential to our understanding of the evolution of North American temperate floras and the nature of Asian North American disjunct taxa.
Newly recognized fossil infructescences and leaves of the Trochodendraceae are described from the Early/ Middle Eocene McAbee and One Mile Creek sites of British Columbia, Canada, and Republic, eastern Washington State, United States. Trochodendron drachukii Pigg, Dillhoff, DeVore, & Wehr sp. nov., from McAbee, is an infructescence similar to that of extant Trochodendron aralioides Sieb. & Zucc. but strongly paniculate rather than racemose. This new species is larger and more robust than those of the Eocene flora of Republic, Washington, and has attached fruits quite similar to both extant Trochodendron Sieb. & Zucc. and Miocene fossils from Asia and western North America. Associated leaves are similar to those of extant Trochodendron except for sometimes bearing short basal auriculate extensions of the lamina. They differ from Trochodendron nastae Pigg, Wehr, & Ickert-Bond leaves from Republic that have palmate rather than pinnate venation. Tetracentron hopkinsii Pigg, Dillhoff, DeVore, & Wehr sp. nov. from One Mile Creek and Tetracentron sp. from Republic have leaves remarkably like those of extant Tetracentron Oliver, firmly establishing the presence of this genus in the Eocene. This study demonstrates that within the Trochodendraceae, a poorly understood group within the eudicot grade, both extinct forms as well as plants with quite modern-appearing fruits and leaves were present by the Eocene in northwestern North America.
Despite previous efforts to elucidate relationships within the Pyreae (Rosaceae), relationships among the major sub-lineages, generic limits, and divergence times have remained uncertain. The present study greatly expands phylogenetic analyses of the Pyreae by using a combination of 11 chloroplast regions plus nuclear ribosomal ITS sequences from 486 individuals representing 331 species and 27 genera. Maximum likelihood and bayesian analyses generally support existing generic boundary, although Sorbus, as previously circumscribed, is clearly non-monophyletic. Two significant conflicts were detected between the chloroplast and ITS phylogenies, suggesting that hybridization played a role in the origins of Micromeles and Pseudocydonia. In addition, we provide estimates of the divergence times of the major lineages. Our findings support the view that the major Pyreae lineages were established during the Eocene-Oligocene period, but that most of the modern diversity did not originate until the Miocene. At least five major, early Old World-New World disjunctions were detected and these vicariance events are generally most consistent with movement through the Beringia.
We report a high-quality draft genome sequence of the domesticated apple (Malus × domestica). We show that a relatively recent (>50 million years ago) genome-wide duplication (GWD) has resulted in the transition from nine ancestral chromosomes to 17 chromosomes in the Pyreae. Traces of older GWDs partly support the monophyly of the ancestral paleohexaploidy of eudicots. Phylogenetic reconstruction of Pyreae and the genus Malus, relative to major Rosaceae taxa, identified the progenitor of the cultivated apple as M. sieversii. Expansion of gene families reported to be involved in fruit development may explain formation of the pome, a Pyreae-specific false fruit that develops by proliferation of the basal part of the sepals, the receptacle. In apple, a subclade of MADS-box genes, normally involved in flower and fruit development, is expanded to include 15 members, as are other gene families involved in Rosaceae-specific metabolism, such as transport and assimilation of sorbitol.
Lyonothamnus Gray is a monotypic genus of evergreen trees endemic to California's Channel Islands. There is one species, L. floribundus, with two subspecies, ssp. floribundus and ssp. asplenifolius. Subspecies floribundus has simple and entire-margined leaves, while leaves of ssp. asplenifolius are pinnate and composed of three to seven primary segments. Despite its restricted modern occurrence, three fossil species have been described from Neogene paleofloras in the far western United States. Lyonothamnus mohavensis Axelrod is known from California; L. parvifolius (Axelrod) Wolfe and L. cedrusensis Axelrod, from Nevada. However, the size ranges used to segregate these species were all found to fall within the range of L. parvifolius from Stewart Valley, Nevada. Study of intact leaves reveals that the combination of (1) number of primary segments, (2) length of primary segments, (3) number of medial secondary segments per primary segment, and (4) lengths and widths of medial secondary segments is important in segregating species. Using these characters, L. parvifolius and L. wolfei Erwin et Schorn sp. nov. are recognized from Nevada and Oregon, and two species, L. mohavensis and L. axelrodii Erwin et Schorn sp. nov., from California. This renewed taxonomy within an updated temporal framework provides an important first step toward understanding the evolution, diversity, paleoecology, and paleobiogeographic history of this unusual member of the Rosaceae.
A new species of Cercocarpus, Cercocarpus mixteca Velasco de León & Cevallos-Ferriz, is described based on leaf impressions from the Los Ahuehuetes locality, near Tepexi de Rodríguez, Puebla, Mexico. The lamina is obovate, 1.3cm in length by 0.5cm in width, has a serrate margin in its distal fourth, craspedodromous venation with a single straight mid-vein and two to four pairs of secondary ones, and areols that tend to be quadrangular in shape. A phenetic analysis of the agglomerative, non-hierarchical type, with mean linkage, is applied using 22 OTUs and 34 character states. The morphological characters observed on the leaves of the new fossil plants support the recognition of a new taxon closely related to the extant Cercocarpus paucidentatus growing naturally in northern Mexico. Its microphyll size corresponds with the temperate to xeric climate postulated for the Los Ahuehuetes locality; this further suggests that some taxa, like Cercocarpus, have a long history in low latitude North America. In this particular case, the extant Cercocarpus fothergilloides and Cercocarpus macrophyllus could, as they were able to colonise new humid and xeric areas, represent descendants of C. mixteca.
Coal-bearing group of rocks of the Nenana coal field in the central part of the Alaska Range is formally subidivided into five new formations, in ascending order-% the Healy Creek, Sanctuary, Suntrana, Lignite Creek, and Grubstake Formations. Fossil leaves and pollen indicate that the coal-bearing group, which is wholly continental, ranges in age from the late Oligocene through the late Miocene. Volcanic glass from the Grubstake Formation has an apparent age of 8. 1 million yr, based on potassium-argon analyses.
Studies of angiosperm leaf cuticles from the Lower Cretaceous Potomac Group reinforce previous evidence for a Cretaceous adaptive radiation of the flowering plants and suggest unsuspected trends in the evolution of stomata and trichomes. Early Potomac Group angiosperm leaf cuticles (Zone I of Brenner or Aptian?) show little interspecific structural diversity, particularly in stomatal organization. All species conform to the same highly plastic pattern of variation in subsidiary cell arrangement, in which the stomata on a single leaf conform to several types, including paracytic, hemiparacytic, anomocytic, laterocytic, and weakly cyclocytic. Several species resemble extant Chloranthaceae and Illiciales, but none represents a modem family. Later leaves (Subzone 11-B of Brenner, or Albian) exhibit greater interspecific structural diversity, particularly in stomatal organization. Three new patterns of variation in subsidiary cell arrangement are present in addition to the older one and each has a subset of the variation present in the older pattern. Cuticular anatomy is consistent with proposed leaf affinities to Platanaceae and Rosidae. The stratigraphic trend in cuticle types supports the concept that the subclass Magnoliidae includes the most primitive living angiosperms. However, it also suggests that the uniformly paracytic stomatal pattern characteristic of Magnoliales, generally considered primitive for the flowering plants, may actually be derived from the variable condition found in Zone I leaves.
A classification of the architectural features of dicot leaves—i.e., the placement and form of those elements constituting the outward expression of leaf structure, including shape, marginal configuration, venation, and gland position—has been developed as the result of an extensive survey of both living and fossil leaves. This system partially incorporates modifications of two earlier classifications: that of Turrill for leaf shape and that of Von Ettingshausen for venation pattern. After categorization of such features as shape of the whole leaf and of the apex and base, leaves are separated into a number of classes depending on the course of their principal venation. Identification of order of venation, which is fundamental to the application of the classification, is determined by size of a vein at its point of origin and to a lesser extent by its behavior in relation to that of other orders. The classification concludes by describing features of the areoles, i.e., the smallest areas of leaf tissue surrounded by veins which form a contiguous field over most of the leaf. Because most taxa of dicots possess consistent patterns of leaf architecture, this rigorous method of describing the features of leaves is of immediate usefulness in both modern and fossil taxonomic studies. In addition, as a result of this method, it is anticipated that leaves will play an increasingly important part in phylogenetic and ecological studies.
Transmontane southern California has a rich, specialized flora and vegetation due to its varied topography, substrata and climate. Of the perhaps 5075 species in 145 vascular plant families indigenous in California, >2100 species in 123 families are represented in transmontane southern California. About 935 species, of which 868 are in the south, 180 of the state's 880 indigenous genera, and 18 families are exclusively or effectively transmontane. Diverse habitats have led to the recognition of 32 different plant communities and 10 subcommunities. A table lists the communities arranged in a hierarchy according to decreasing altitude from alpine through subalpine, montane, and transition to desert and alkaline scrub communities. These are each discussed briefly with comments on distribution, dominant or otherwise characteristic plants, and outstanding environmental features of the habitats occupied.-from Author
A flora from Tertiary fossiliferous shales of the upper part of the Ruby Basin in southwestern Montana is described. The intermontane lacustrine deposits consist of two phases with distinct floral assemblages. The composite flora comprises aquatic, riparian temperate deciduous- and coniferous-forest, xeric-woodland, and desert-scrub associations. The flora consists of 37 families, 61 genera, and 82 identifiable species of which 25 are heretofore undescribed. Three additional new species are described among the Incertae sedis. Approximately 12 per cent of the species are gymnosperms, and 85 per cent are angiosperms. Arcto-Tertiary and Madro-Tertiary elements are equally represented. Comparison with the Bridge Creek and Green River floras discloses a 13 per cent and 4.5 per cent respective overlap. Significantly, a 40 per cent specific identity exists between the Ruby and Florissant floras. Nearly identical floristic units suggest that the Ruby and Florissant floral assemblages were part of a single botanical province. The fossiliferous shales of the Ruby area are late Oligocene and nearly contemporaneous with the Bridge Creek shales but younger than those of the Florissant area. The Recent flora is chiefly xeric-semidesert, xeric-coniferous, Hudsonian-deciduous, and Hudsonian-coniferous.
Six drainage basins at the margins of Trinity Lake were analyzed to determine the relations of source vegetation (largely coniferous forest) to plant debris in deltaic deposits that represent high-energy depositional environments. Thirty-one samples containing an estimated 1 043 000 identifiable plant fragments were subjected to a multivariate statistical (correspondence) analysis; in the resulting ordination, samples from the more mesic side of the lake clustered separately from samples from the drier side of the lake. The information gained from the Trinity analysis is compared to information gained from analysis of plant debris in low-energy depositional environments. Whereas high-energy environments contain the best taxonomic representation of source vegetation, low-energy environments retain information on spatial distributions of taxa within source vegetation. High-energy environments typically also contain the best representation of different organs of a given taxon. -from Authors
Fossil angiosperm leaves and other remains from the Middle Eocene Allenby Formation, at One Mile Creek near Princeton, southern British Columbia, are described and assigned to Betula leopoldae Wolfe & Wehr. Based on association evidence and independently determined systematic relationships, we suggest that the vegetative and reproductive structures were produced by a single fossil species. Combined information from all the organs available suggests that this Eocene Betula is most closely related to species in section Eubetula, subsection Costatae of the extant genus. Material from One Mile Creek constitutes the earliest fully documented record of the genus Betula based on both vegetative and reproductive structures. In the context of the fossil history of the Betulaceae as a whole, it indicates that the two extant genera of the Betuleae, Alnus and Betula, were clearly differentiated by the Middle Eocene. -from Authors
In Mediterranean southern California, 26 families (17 reported for the first time) have vasicentric tracheids; notable genera include Arctostaphylos, Ceanothus, Prunus, Quercus and Salvia. Desert shrubs have vasicentric tracheids to a somewhat lesser degree. -from Author
Coherent patterns of morphology of apparent value in determining taxonomic and phylogenetic relationships are present in dicotyledonous leaves. Features of greatest value in assessing these affinities include leaf organization; marginal features, including morphology of the tooth; major vein configuration; characters of the intercostal venation; and gland placement. Of these, recognition of tooth morphology appears to be an overlooked tool of major systematic importance. Variation in these features is most coherent when analyzed in terms of the Takhtajan and Cronquist systems of dicot classification. Essential to our procedure was a recognition of the "basic" leaf features of each taxon. These were regarded as the most generalized type from which all of the more specialized types in a taxon could have been derived and they were derived from an analysis of the comparative morphology of modern leaves with limited input from the fossil record. The resulting scheme indicates strong correlation of leaf features with six of the seven Takhtajan subclasses, in addition to paralleling and clarifying both systems at the ordinal and familial levels. Conspicuous exceptions are the breakdown of the Asteridae into a possible rosid and a possible dilleniid group, reassignment of the Celastrales and Myrtales to the Dilleniidae, and of the Juglandales to the Rosidae. Affinities of numerous problem taxa, such as the Didymelaceae and Medusagynaceae, are resolved, as are some of the points of disagreement between the Takhtajan and Cronquist arrangements. This analysis also provides the first systematic summary of dicot leaf architectural features and the outlines of a regular systematic method for leaf determination.
A B S T R A C T A classification of the architectural features of dicot leaves-i.e., the placement and form of those elements constituting the outward expression of leaf structure, including shape, marginal configuration, venation, and gland position-has been developed as the result of an extensive survey of both living and fossil leaves. This system partially incorporates modifications of two earlier classifications: that of Turrill for leaf shape and that of Von Ettingshausen for venation pattern. After categorization of such features as shape of the whole leaf and of the apex and base, leaves are separated into a number of classes depending on the course of their principal venation. Identification of order of venation, which is fundamental to the application of the classification, is determined by size of a vein at its point of origin and to a lesser extent by its behavior in relation to that of other orders. The classification concludes by describing features of the areoles, i.e., the smallest areas of leaf tissue surrounded by veins which form a contiguous field over most of the leaf. Because most taxa of dicots possess consistent patterns of leaf architecture, this rigorous method of describing the features of leaves is of immediate usefulness in both modern and fossil taxonomic studies. In addition, as a result of this method, it is anticipated that leaves will play an increasingly important part in phylogenetic and ecological studies.
The vegetation types of the Tertiary are analyzed in terms of latitude, altitude, and orographic positions and from continental and maritime climatic regimes. The relationships between temperature and vegetation is studied. The leaf assemblages of the vegetation and the effect of plate tectonics on the location of the assemblages are examined. The vegetation observed globally at various latitudes in the Paleocene, Eocene, Oligocene, and Neogene forests are described.
On theoretical grounds, an analysis of the physiognomy of a Tertiary leaf assemblage is more direct and reliable than a circuitous floristic analysis in assigning thermal regimes to fossil assemblages. Using primarily foliar physiognomy and secondarily floristic composition, it can be shown that: (1) some middle latitude Tertiary assemblages probably lived under meteoroligically tropical climates; (2) a major and rapid climatic deterioration occurred in the Oligocene; and (3) a major climatic fluctuation probably occurred in the Late Eocene.These analyses thus substantiate the conclusions of several other paleobotanists regarding climatic fluctuations. Recent criticisms of these analyses are shown to be invalid and to be based largely on misinterpretations.
Our attempt at putatively phylogenetic classifications of Angiospermae, considering our vast ignorance of more than 120 million years of evolution of the class, must be very tentative and elastic to make full use of the new approaches and new data constantly being made available to us. Some of the realignments thus required in my system of classification are here explained. Among others, the Paeoniales are recognized and include Glaucidiaceae; various shifts of families are made within Thei–florae–Violiflorae–Malviflorae; Thymelaeaceae and Simmondsiaceae are transferred to Euphorbiales; Emblingiaceae, Gyrostemonaceae and Bataceae are added to Sapindineae; Fabineae, with Connaraceae, Surianaceae and Fabaceae, are transferred to Rutiflorae; Proteiflorae are placed near Rutiflorae, especially Fabineae; the largely Australasian–African Pittosporales are explained; Cornaceae are severely pruned; Haemodoraceae and Velloziaceae are transferred to Commelinales; Arecales, Cyclanthales and Pandanales are separated into unrelated superorders; and Typhiflorae are moved into closer proximity with Commeliniflorae.
Rate of herbivory and defensive characteristics of young and mature leaves were measured for saplings of 46 canopy tree species in a lowland tropical rain forest (Barro Colorado Island, Panama). Grazing rates were determined in the field for sample periods in the early wet, late wet, and dry seasons. Leaf properties such as pubescence, toughness, water, protein, fiber, and phenolic contents explained over 70% of the variation among plant species in the rates of herbivory on mature leaves. Leaf toughness was most highly correlated with levels of herbivory, followed by fiber content and nutritive value. Phenol content and phenol : protein ratios were not significantly correlated with damage. Journal Article
The known fossil fruits and leaves of Acer from western North America represent 91 species and 28 sections, 12 of which are extinct and are described as new sections of Acer. Sixty-four species are described as new, 2 new combinations are proposed, and 6 species are left unnamed; 21 have been previously described. The most diverse sections of Acer in the Tertiary of western North America are the extinct Glabroidea (at least 13 species), Negundo (9 species), Macrophylla (8 species), and Eriocarpa (8 species), Descriptions of almost all the species are presented, and all species are illustrated. Although Aceraceae are considered to be derivatives of an early, extinct group of Sapindaceae, Paullinieae (rather than Harpullieae) are considered 10 be the extant tribe of Sapindaceae most closely related 10 Aceraceae. A cladistic analysis of Aceraceae and of Acer includes Sapindaceae, Dipteronia, and the "Acer" arcticum complex, which is thought to represent an extinct genus of Aceraceae. The cladistic analysis based on extant Acer results in the subdivision of Acer into 4 informal groups: Spicata Group, Macrantha Group, Macrophylla Group (including section Acer and allies), and the Platanoidea Group. Timing of first appearances of the various groups and sections in the fossil record generally parallel the cladistic analysis. The Spicata Group is the oldest (latest Paleocene); this group includes three extinct sections in the early middle Eocene, all of which became extinct by the late middle Eocene. First known in the early middle Eocene are extinct sections of the Macrantha and Macrophylla groups; extant sections of these groups appear by the late middle to early late Eocene. The Platanoidea Group appeared in the late middle Eocene, and extant sections appeared by the latest Eocene. A fifth group, the Orba Group, is known only as fossil and represents sections that diverged between the divergences of the Macrantha and Macrophylla groups. Diversification of Acer at the sectional level appears to have taken place in a volcanic upland region in western North America during the Eocene. Although possibly a mesothermal genus during the late Paleocene and early Eocene, Acer diversified greatly during the middle and late Eocene as microthermal climates increased in area. During the early middle Eocene, 10 sections (all extinct) and 11 species of Acer are known. During the late middle to late Eocene, Acer reached maximal diversity in western North America: at least 34 species and 15 sections are known, and occurrences of other species and sections can be inferred. Acer, however, was apparently a very minor element in Eocene microthermal vegetation. Sectional diversification of Acer was largely completed by the end of the Eocene, although a few derivative sections may be of post-Eocene age. Acer reached maximum abundance in western North America during the early and middle Miocene: at least 29 species and 10 sections are known. Following the middle Miocene, Acer underwent a major decline in diversity and abundance in western North America; this decline was due primarily to declining summer temperatures at high latitudes and increasing aridity at middle latitudes. Present distributions of sections and species of Acer have resulted from a complex history of dispersals and vicariant events, most of which are related to climate. Probable origin of many extant Asian sections of Acer in western North America during the Eocene implies many dispersals from North America to Asia during the Eocene. Many extinct and extant sections of Acer became extinct on North America during the late Eocene and early Oligocene; some of these extant sections re-entered North America during the late Oligocene and Miocene but again became extinct during the Miocene. Cladistic relationships of series Saccharodendron strongly indicate an origin in western Eurasia. Appearance of this section in North America during the early Miocene and absence of a Beringian fossil record indicate long-distance dispersal across the Atlantic Ocean. Absence of a Tertiary record in western North America of Palmata indicates a long-distance dispersal from eastern Asia.
Plates preceded by guard sheets with descriptive letterpress. Thesis (Ph. D. in Botany)--University of California, Berkeley, Sept. 1938. Includes bibliographical references. Microfilm. s
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