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After the Ice Age: The Return of Life to Glaciated North America
Abstract
The fascinating story of how a harsh terrain that resembled modern Antarctica has been transformed gradually into the forests, grasslands, and wetlands we know today. "One of the best scientific books published in the last ten years."âOttowa Journal "A valuable new synthesis of facts and ideas about climate, geography, and life during the past 20,000 years. More important, the book conveys an intimate appreciation of the rich variety of nature through time."âS. David Webb,Science
... As subsequent glacial advances erased many traces of conditions at ice margins, paleoecological reconstructions of proglacial lakes are mostly limited to conditions during late and end stages of the Wisconsinan glaciation (e.g., Teller and Clayton 1983;McAllister et al. 1988;Karrow et al. 2001). Vivid reconstructions of proglacial lake conditions are provided by Pielou (1991), Power (2002), and Carrivick and Tweed (2013). Proglacial lakes varied considerably in size and likely underwent different dynamic processes during glacial advance, maxima, and retreat (Carrivick and Tweed 2013), with some dwarfing contemporary freshwater lakes (Teller and Clayton 1983;Dawson 1992). ...
... Lakes shifted in size, extent, and location with movements of glacial fronts, ice streams, and neighboring topography (Ashley 2002;Carrivick and Tweed 2013), and were subject to rapid and sometimes catastrophic drainage or changes in depth. Some of the best known recent examples toward the end of the Pleistocene were the emptying of Glacial Lake Missoula, the abrupt drainage of Glacial Lake Algonquin via spillways to the St. Lawrence River and formation of the Champlain Sea, and the emptying of Glacial Lake Agassiz and Barlow-Ojibway when the Laurentian Ice Dome collapsed over Hudson Bay (Pielou 1991). ...
... Once isolated, the same ecological and demographic constraints described earlier would have limited local population sizes (Martin and Olver 1980;Mills et al. 2002), with subsequent effects on N e and population divergence (Hill 2018;Wellband et al. 2021). These conditions may have been more pronounced during the warmer Hypsithermal interval approximately 8.5-6 kya (Pielou 1991;Teller et al. 2017), but many lake charr populations were able to persist for millennia in the absence of harvest exploitation and competition from warmer-water species. ...
The lake charr Salvelinus namaycush is an archetypal cold-water species closely associated with Pleistocene glaciations. Although repeated glaciations destroyed most traces of the species’ zoogeographic history, its evolutionary and paleoecological legacy can be inferred from its biological attributes. Lake charr fossils are rare, but molecular evidence suggests the species diverged from other charrs during the late Pliocene or early Pleistocene. The lake charr differs from other charrs by its large size, longevity, extreme iteroparity, top predator specialization, reduced sexual dimorphism, and deepwater habitat. Ecological parallels between the lake charr and the taimen Hucho taimen suggest the lake charr may have originated as a large-bodied predator in Pliocene rivers, with subsequent lakes formed by glacial expansion and retreat providing novel ecological opportunities. Specialization as an apex predator for oligotrophic environments likely selected for longevity and iteroparity. Exploitation of benthic foods opened new opportunities largely unexploited by other charrs that drove other divergent traits such as vision, coloration, buoyancy, reduced sexual dimorphism, and spawning behavior. Although glacial refugia were highly dynamic environments, lake charr specialized for these conditions persisted in multiple refugia through several glacial cycles. Dispersal from Wisconsinan refugia enabled rapid colonization via vast meltwater lakes into its contemporary range.
... than was observed by Kyle and Strobeck (2003) between Golden, British Columbia (northern portion of our study area) and the island of Newfoundland (F ST = 0.21, Kyle and Strobeck, 2003). In addition to lying 4,000 km to the east, Newfoundland has not had a terrestrial connection with the rest of North America since the end of the Pleistocene glaciations (Pielou, 2008). During the last glacial maximum, approximately 20,000 years before present (Clark et al., 2009), the Clark Fork Valley along with the CDA Mountains were part of the large, 300 km long, Lake Missoula (Pielou, 2008). ...
... In addition to lying 4,000 km to the east, Newfoundland has not had a terrestrial connection with the rest of North America since the end of the Pleistocene glaciations (Pielou, 2008). During the last glacial maximum, approximately 20,000 years before present (Clark et al., 2009), the Clark Fork Valley along with the CDA Mountains were part of the large, 300 km long, Lake Missoula (Pielou, 2008). North of Lake Missoula, our study area was largely engulfed by the Cordilleran Ice Sheet (Pielou, 2008) with the remaining southern portion of our study area being ice free and part of the Pacific Northwest Refugium (Shafer et al., 2010). ...
... During the last glacial maximum, approximately 20,000 years before present (Clark et al., 2009), the Clark Fork Valley along with the CDA Mountains were part of the large, 300 km long, Lake Missoula (Pielou, 2008). North of Lake Missoula, our study area was largely engulfed by the Cordilleran Ice Sheet (Pielou, 2008) with the remaining southern portion of our study area being ice free and part of the Pacific Northwest Refugium (Shafer et al., 2010). M. caurina are among the 150 known species or species complexes that have disjunct mesic forest inland and coastal populations in Pacific Northwest (Carstens et al., 2004) due to desertification of the Columbia Plateau (Shafer et al., 2010). ...
North American martens are forest dependent, influenced by human activity, and climate vulnerable. They have long been managed and harvested throughout their range as the American marten (Martes americana). Recent work has expanded evidence for the original description of two species in North America — M. americana and the Pacific Coast marten, M. caurina — but the geographic boundary between these groups has not been described in detail. From 2010 to 2016 we deployed 734 multi-taxa winter bait stations across a 53,474 km² study area spanning seven mountain ranges within the anticipated contact zone along the border of Canada and the United States. We collected marten hair samples and developed genotypes for 15 polymorphic microsatellite loci for 235 individuals, and 493 base-pair sequences of the mtDNA gene COI for 175 of those individuals. Both nuclear and mitochondrial genetic structure identified a sharp break across the Clark Fork Valley, United States with M. americana and M. caurina occurring north and south of the break, respectively. We estimated global effective population size (Ne) for each mountain range, clinal genetic neighborhood sizes (NS), calculated observed (Ho) and expected (He) heterozygosity, fixation index (FST), and clinal measures of allelic richness (Ar), Ho, and inbreeding coefficient (FIS). Despite substantial genetic structure, we detected hybridization along the fracture zone with both contemporary (nuclear DNA) and historic (mtDNA) gene flow. Marten populations in our study area are highly structured and the break across the fracture zone being the largest documented in North America (FST range 0.21–0.34, mean = 0.27). With the exception of the Coeur d’Alene Mountains, marten were well distributed across higher elevation portions of our sampling area. Clinal NS values were variable suggesting substantial heterogeneity in marten density and movement. For both M. americana and M. caurina, elevationaly dependent gene flow and high genetic population structure suggest that connectivity corridors will be important to ensuring long-term population persistence. Our study is an example of how a combination of global and clinal molecular data analyses can provide important information for natural resource management.
... Such a pattern may be a result of responses of the Sheepnose to climate change oscillations during the Pleistocene (Alberdi et al., 2015). North American freshwater systems were heavily impacted by the expansion and contraction of Pleistocene glaciers, and the population structure of freshwater organisms often reflect these events (Berendzen et al., 2010;Inoue & Berg, 2017;Inoue et al., 2014;Jones et al., 2015;Mathias et al., 2016;Pielou, 2008 (Hewitt, 1996(Hewitt, , 2000Inoue et al., 2014;Pielou, 2008;Stewart & Lister, 2001). ...
... Such a pattern may be a result of responses of the Sheepnose to climate change oscillations during the Pleistocene (Alberdi et al., 2015). North American freshwater systems were heavily impacted by the expansion and contraction of Pleistocene glaciers, and the population structure of freshwater organisms often reflect these events (Berendzen et al., 2010;Inoue & Berg, 2017;Inoue et al., 2014;Jones et al., 2015;Mathias et al., 2016;Pielou, 2008 (Hewitt, 1996(Hewitt, , 2000Inoue et al., 2014;Pielou, 2008;Stewart & Lister, 2001). ...
North American freshwater mussel species have experienced substantial range fragmentation and population reductions. These impacts have the potential to reduce genetic connectivity among populations and increase the risk of losing genetic diversity. Thirteen microsatellite loci and an 883 bp fragment of the mitochondrial ND1 gene were used to assess genetic diversity, population structure, contemporary migration rates, and population size changes across the range of the Sheepnose mussel (Plethobasus cyphyus). Population structure analyses reveal five populations, three in the Upper Mississippi River Basin and two in the Ohio River Basin. Sampling locations exhibit a high degree of genetic diversity and contemporary migration estimates indicate that migration within river basins is occurring, although at low rates, but there is no migration is occurring between the Ohio and Mississippi river basins. No evidence of bottlenecks was detected, and almost all locations exhibited the signature of population expansion. Our results indicate that although anthropogenic activity has altered the landscape across the range of the Sheepnose, these activities have yet to be reflected in losses of genetic diversity. Efforts to conserve Sheepnose populations should focus on maintaining existing habitats and fostering genetic connectivity between extant demes to conserve remaining genetic diversity for future viable populations. Population genetic analyses of the Sheepnose mussel reveal five populations. Sampling locations exhibit a high degree of genetic diversity and contemporary migration estimates indicate that migration between populations within river basins is occurring, although at low rates. But no migration is occurring between the Ohio and Mississippi river basins.
... Pleistocene glaciation events had a great impact on the Arctic fishes through population movement during glacial maxima and subsequent recolonizations of contemporary ranges after the ice sheets have receded (Lindsey & McPhail, 1986;Pielou, 1991). Ice sheets physically isolated populations into separate glacial refugia where they could undergo allopatric divergence for thousands of years (Shafer et al., 2010). ...
... The geographical location of the current charr contact zones on both sides of the Pacific Ocean fits well into the entire pattern of the natural hybrid zone distribution of the salmonids (Taylor, 2004) associated with the formation of the ice shields in the Pleistocene (Pielou, 1991). Populations of the lake charrs from the Arctic regions of northeastern Asia also fall within this zone. ...
en Many lacustrine charrs of the genus Salvelinus were described as separate species, and their origin and phylogenetic relationships are still under debate. In this study, we described the genetic variation of charrs from Lake Grand (Elikchan Lake Group, the mainland coast of the Sea of Okhotsk, Russia) and several locations outside of this system based on eight microsatellite (ms) loci and mitochondrial (mt) DNA control region. We tested the hypothesis of the resident charr membership to (a) the Arctic lineage of Salvelinus taranetzi sensu (Oleinik et al., Russian Journal of Genetics, 51, 2015, 55); (b) the Bering lineage of the Northern Dolly Varden Salvelinus malma malma; and (c) the Atlantic lineage of the Arctic charr Salvelinus alpinus. Analysis of phylogenetic relationships based on the mtDNA control region showed that all individuals from Lake Grand grouped with the Bering lineage. Bayesian analysis using msDNA supports the clustering together of charrs from Lake Grand and Arctic lineage, regardless of their mtDNA haplotypes. Incongruence between mtDNA and msDNA markers provided strong evidence of historical mtDNA introgression from S. malma malma to S. taranetzi. Patterns of divergence confirm a postglacial secondary contact of the representatives of Arctic and Bering lineages in the area of the Sea of Okhotsk coast and past hybridization in Lake Grand with the following features: (a) complete fixation of introgressed mtDNA of one species within populations of another and (b) absence of modern population of S. malma malma in the lake.
Abstracto
es El origen y las relaciones filogenéticas de los salvelinos lacustres del género Salvelinus, muchos de los cuales se han descrito como especies separadas, se están debatiendo actualmente de una forma activa. En este estudio, describimos la variabilidad genética de los salvelinos del lago Grand (el sistema de los lagos de Elikchan en la costa continental del mar de Okhotsk, Rusia) y varias ubicaciones fuera de este sistema, en base a ocho locuses de microsatélites (ms) y una región de control del ADN mitocondrial (mt). Probamos la hipótesis de que el salvelino lacustre pertenece al (1) linaje Arctic del Salvelinus taranetzi sensu Oleinik et al. (2015); (2) linaje Bering del Salvelinus malma malma; (3) linaje Atlantic del Salvelinus alpinus. El análisis de las relaciones filogenéticas basadas en la región de control del mtADN mostró que todos los salvelinos del lago Grand pertenecen al linaje Bering. El análisis bayesiano utilizando msADN admite la la agrupación de salvelinos del lago Grand y el linaje Arctic, independientemente del haplotipo de mtADN. El desajuste entre los marcadores mtADN y msADN ha proporcionado una fuerte evidencia de la introgresión histórica del mtADN de S. malma malma a S. taranetzi. Los modelos de la divergencia detectada confirman el contacto secundario post-glacial de representantes de los linajes Arctic y Bering en la región de la costa del mar de Okhotsk, así como la hibridación histórica en el lago Grand con las siguientes características: (1) fijación completa de mtADN introgresado de una especie en poblaciones de otra; (2) la ausencia de la población moderna de S. malma malma en el lago.
... In semi-arid ecosystems of the south-central United States (e.g., south Texas) and northern Mexico, extreme freeze events dictate the northern distribution of many tropical plant species, including native woody plant species like great leadtree (Leucaena pulverulenta), anacahuita (Cordia boissieri), and coyotillo (Karwinskia humboldtiana; Bojórquez et al., 2019;Lonard & Judd, 1985, 1991. In the more humid and seasonal wet-dry ecosystems of south and central Florida, extreme freeze events govern the northern distribution of entire forest biomes (Greller, 1980) as well as the range limits of plant species such as poisonwood (Metopium toxiferum), gumbo limbo (Bursera simaruba), cocoplum (Chrysobalanus icaco), and pigeon plum (Coccoloba diversifolia; Box et al., 1993;Myers, 1986;Olmsted et al., 1993). ...
... Since the last glacial maximum about 19,000 years ago, warming temperatures have allowed cold-sensitive tropical organisms to move northward to their current northern range limits in North America (Pielou, 1991;Woodroffe & Grindrod, 1991;Zink & Gardner, 2017). Many of these species have traveled large distances (~2000-3000 km) as they adjusted to a warming world. ...
... tergenimus over both long-and short term timescales. Over evolutionary timescales (1000's of years), a coalescent-based PSMC analysis shows that for much of the last 100,000 years S. catenatus has consistently had an effective size that is > 2 -3X smaller than S. tergeminus even in the face of shifting distributions due to impacts of ice sheet expansion and contraction during the late Pleistocene (Pielou, 1992). Fundamental differences in the ecology of these species may account for the long-term differences in effective size. ...
... tergeminus . This timeframe coincides with the colonization and subsequent landscape modification by European settlers in North America (Pielou, 1992;Schmidt, 1938) which has resulted in the habitat destruction and fragmentation that has played a key role in recent range-wide declines of S. catenatus (Szymanski et al., 2016). Overall our analyses provide new historical evidence in support of the idea that anthropogenic impacts have had a consistently greater impact on S. catenatus. ...
Theory predicts that threatened species living in small populations will experience high levels of inbreeding that will increase their negative genetic load but recent work suggests that the impact of load may be minimized by purging resulting from long term population bottlenecks. Empirical studies that examine this idea using genome-wide estimates of inbreeding and genetic load in threatened species are limited. Here we use genome resequencing data to compare levels of inbreeding, levels of genetic load and population history in threatened Eastern massasauga rattlesnakes (Sistrurus catenatus) which exist in small isolated populations and closely-related yet outbred Western massasauga rattlesnakes (S. tergeminus). In terms of inbreeding, S. catenatus genomes had a greater number of ROHs of varying sizes indicating sustained inbreeding through repeated bottlenecks when compared to S. tergeminus. At the species level, outbred S. tergeminus had higher genome-wide levels of genetic load in the form of greater numbers of derived deleterious mutations compared to S. catenatus presumably due to long-term purging of deleterious mutations in S. catenatus. In contrast, mutations that escaped the “drift sieve” and were polymorphic within S. catenatus populations were more abundant and more often found in homozygote genotypes than in S. tergeminus suggesting a reduced efficiency of purifying selection in smaller S. catenatus populations. Our results support an emerging idea that the historical demography of a threatened species has a significant impact on the type of genetic load present which impacts implementation of conservation actions such as genetic rescue.
... The shifting environments that occurred with the retreat of continental ice sheets at the end of the last glacial period provided opportunities for secondary contact and hybridization in many taxa. As the continental ice sheets began retreating, 18-20 kya, they created new habitats which species colonized (Pielou 1991). In North America, the Laurentian Great Lakes were formed and species that survived in refugia during the glaciation followed the ice edges, colonizing the newly created habitat (Pielou 1991;Graf 1997Graf , 2002. ...
... As the continental ice sheets began retreating, 18-20 kya, they created new habitats which species colonized (Pielou 1991). In North America, the Laurentian Great Lakes were formed and species that survived in refugia during the glaciation followed the ice edges, colonizing the newly created habitat (Pielou 1991;Graf 1997Graf , 2002. Post-glacial species range expansions led to secondary contact of formerly isolated populations and species, and if reproductive barriers were incomplete, gene flow may have occurred (hybridization with or without introgression). ...
Correct species identification and delineation are crucial for effective conservation and management. However, species delineation can be problematic in the presence of morphological ambiguities due to phenotypic plasticity, convergence, and/or interspecific hybridization. Here, we investigated the degree of hybridization between two closely related freshwater mussel species [Bivalvia: Unionidae; Lampsilis siliquoidea (Barnes) and L. radiata (Gmelin)] that present intermediate forms in areas of sympatry. Unionids have a distinct form of mitochondrial DNA (mtDNA) inheritance, termed doubly uniparental inheritance (DUI) where female mtDNA (F-type) is transmitted to all progeny but male mtDNA (M-type) is mostly inherited by the males resulting in mostly homoplasmic females and heteroplasmic males. An individual was identified as hybrid when F-type and M-type mtDNA of the two different species were found in the same individual. Twelve out of 116 sequenced males were identified as hybrids indicating that these species hybridize where their geographic range overlaps in the lower Great Lakes and St. Lawrence basins. Microsatellite analyses further support the occurrence of hybridization but at a larger spatial scale than indicated by the mitochondrial analyses. We also found that strong within-species population genetic structure affects the detection of purebred individuals overestimating the number of hybrids. Given the large geographic scale and proportion of hybrids found in this study, natural hybridization and introgression need to be considered when implementing local biodiversity inventories, identifying waterbodies as source of organisms for relocation and restoration projects and when setting appropriate conservation policies.
... In semi-arid ecosystems of the south-central United States (e.g., south Texas) and northern Mexico, extreme freeze events dictate the northern distribution of many tropical plant species, including native woody plant species like great leadtree (Leucaena pulverulenta), anacahuita (Cordia boissieri), and coyotillo (Karwinskia humboldtiana; Bojórquez et al., 2019;Lonard & Judd, 1985, 1991. In the more humid and seasonal wet-dry ecosystems of south and central Florida, extreme freeze events govern the northern distribution of entire forest biomes (Greller, 1980) as well as the range limits of plant species such as poisonwood (Metopium toxiferum), gumbo limbo (Bursera simaruba), cocoplum (Chrysobalanus icaco), and pigeon plum (Coccoloba diversifolia; Box et al., 1993;Myers, 1986;Olmsted et al., 1993). ...
... Since the last glacial maximum about 19,000 years ago, warming temperatures have allowed cold-sensitive tropical organisms to move northward to their current northern range limits in North America (Pielou, 1991;Woodroffe & Grindrod, 1991;Zink & Gardner, 2017). Many of these species have traveled large distances (~2000-3000 km) as they adjusted to a warming world. ...
Tropicalization is a term used to describe the transformation of temperate ecosystems by poleward‐moving tropical organisms in response to warming temperatures. In North America, decreases in the frequency and intensity of extreme winter cold events are expected to allow the poleward range expansion of many cold‐sensitive tropical organisms, sometimes at the expense of temperate organisms. Although ecologists have long noted the critical ecological role of winter cold temperature extremes in tropical‐temperate transition zones, the ecological effects of extreme cold events have been understudied, and the influence of warming winter temperatures has too often been left out of climate change vulnerability assessments. Here, we examine the influence of extreme cold events on the northward range limits of a diverse group of tropical organisms, including terrestrial plants, coastal wetland plants, coastal fishes, sea turtles, terrestrial reptiles, amphibians, manatees, and insects. For these organisms, extreme cold events can lead to major physiological damage or landscape‐scale mass mortality. Conversely, the absence of extreme cold events can foster population growth, range expansion, and ecological regime shifts. We discuss the effects of warming winters on species and ecosystems in tropical‐temperate transition zones. In the twenty‐first century, climate change‐induced decreases in the frequency and intensity of extreme cold events are expected to facilitate the poleward range expansion of many tropical species. Our review highlights critical knowledge gaps for advancing understanding of the ecological implications of the tropicalization of temperate ecosystems in North America.
... Great Bear Lake (Northwest Territories, Canada), spanning the Arctic Circle, provides an excellent opportunity to investigate the role of among-individual diet variation in diversification processes in postglacial lakes ( Figure 1). Here, lake trout, Salvelinus namaycush, show a high degree of intraspecific diversity within a geologically young system (8,000-10,000 yr BP; Johnson, 1975;Pielou, 2008). ...
... McConnell 8,000-10,000 yr BP (Johnson, 1975;Pielou, 2008). The lake has characteristics typical of an arctic lake: ultra-oligotrophic, short ice-free season, and a simple food web supporting only 15 fish species (Alfonso, 2004;Johnson, 1975;MacDonald et al., 2004). ...
In a polyphenic species, differences in resource use are expected among ecotypes, and homogeneity in resource use is expected within an ecotype. Yet, using a broad resource spectrum has been identified as a strategy for fishes living in unproductive northern environments, where food is patchily distributed and ephemeral. We investigated whether specialization of trophic resources by individuals occurred within the generalist piscivore ecotype of lake trout from Great Bear Lake, Canada, reflective of a form of diversity. Four distinct dietary patterns of resource use within this lake trout ecotype were detected from fatty acid composition, with some variation linked to spatial patterns within Great Bear Lake. Feeding habits of different groups within the ecotype were not associated with detectable morphological or genetic differentiation, suggesting that behavioral plasticity caused the trophic differences. A low level of genetic differentiation was detected between exceptionally large-sized individuals and other piscivore individuals. We demonstrated that individual trophic specialization can occur within an ecotype inhabiting a geologically young system (8,000-10,000 yr BP), a lake that sustains high levels of phenotypic diversity of lake trout overall. The characterization of niche use among individuals, as done in this study, is necessary to understand the role that individual variation can play at the beginning of differentiation processes.
... With a warming and drier climate, H. c. columbia spread further north and east, establishing its current range in the Northeast and Great Lakes region on its preferred larval host, the eastern Larix laricina (Du Roi, 1771) K. Koch, 1873. The prairie potholes of the Dakotas are remnant tamarack bogs, evidence of shifting plant distributions in the immediate post-Ice Age (Watts and Bright 1968;Pielou 1991). ...
Hybridization and genetic introgression during the speciation process are now believed to be widespread among many animal groups. Extensive hybrid zones and hybrid introgression in Hyalophora are interpreted in relation to these species and speciation concepts. Historical and current evolutionary studies of Hyalophora, and consequent taxonomic revisions, are reviewed. We emphasize those named (e.g., H. “kasloensis”) and unnamed taxa and populations of apparent hybrid origin. A COI phylogenetic analysis of the genus is presented. Hyalophora cecropia shows minimal haplotype divergence over its distribution and does not form hybrid zones in areas of range overlap with congeners. Hyalophora euryalus also shows minimal genetic divergence despite a large West Coast distribution, where it occupies a diversity of plant communities. By contrast, H. columbia gloveri is subdivided into extensive Great Basin and Rocky Mountain haplotype groups. Hyalophora columbia gloveri is distinguished from H. c. columbia by the smallest haplotype divergence of any inter-taxon comparison. We found a shared haplotype between these subspecies from populations located in the northern Rocky Mountains and Minnesota, respectively. The genetic break between eastern and western H. c. columbia populations mirrors a transition zone seen in morphological and ecological characters that is found in eastern Manitoba and western Ontario. Extensive hybridization occurs wherever H. euryalus and H. c. gloveri overlap, varying from narrow hybrid zones to geographically extensive, self-sustaining populations of exclusively hybrid individuals. Several cases of mitochondrial capture were discovered, in which the predominant haplotype of H. euryalus was incorporated at high frequency in both hybrid populations and populations of phenotypically “pure” H. c. gloveri. Newfound larval and adult phenotypic geographic variation is documented and discussed in terms of a possible origin in hybridization and introgression. Select populations are evaluated as possible examples of hybrid species.
... The most recent large-scale ice age, during the Pleistocene Epoch, ended around 11,700 years ago, and led to a range of species' responses, particularly in North America (Lister, 2004;Pearson, 2013;Bibi and Kiessling, 2015;Puzachenko and Markova, 2019). During the Last Glacial Maximum, two major refugia existed in western North America: Beringia and the Pacific Northwest (Hultén, 1937;Pielou, 1991). While those areas are widely accepted as refugia for species during this ice age, there is evidence of additional, smaller refugia along coastal Alaska and British Columbia (Shafer et al., 2010). ...
Human disturbance and climate change can impact populations by disrupting movement corridors and reducing important habitat. Characterizing how animals respond to such environmental changes is valuable for conservation as many species can experience reduced genetic diversity when deleterious habitat change occurs, leading to an increased likelihood of extirpation. Mountain goats (Oreamnos americanus) exemplify this conservation challenge; their geographically isolated habitat can inhibit gene flow, making them susceptible to population declines in the face of anthropogenic-induced change. To facilitate biologically informed population management of mountain goats in Glacier Bay National Park, Alaska, we characterized the fine-scale genetic population structure and examined how future climate change could impact population density. Our results indicated that three genetically distinct subpopulations exist in Glacier Bay and that the genealogical history is reflective of the historic landscape patterns. Climate modeling predicted that demographic productivity was likely to be reduced for all subpopulations; additionally, we found that climate change likely degrades the suitability of movement corridors that facilitate gene flow between subpopulations, ultimately increasing the cost of travel. Understanding such fine-scale patterns are key to managing subpopulations, particularly with impending changes to the landscape.
... This leaves two plausible scenarios: (1) after the LGM, canutus spread from Europe to colonize the Nearctic breeding range of islandica, and then gave rise to rufa through a southward expansion from Ellesmere Island; or (2) the rufa/islandica clade arose in situ from a Nearctic refugium. The former scenario is possibly consistent with estimates of F ST (Table 1) It is well established that a huge swath of the Arctic including most of Beringia and stretching westward almost to the Taimyr Peninsula in central Russia was largely ice-free at the LGM (Ehlers & Gibbard, 2007;Pielou, 1991), and this refugium probably gave rise to all Palearctic and Beringian red knot populations. Meanwhile, the Nearctic was predominantly glaciated at the LGM, including nearly all of the present-day breeding ranges of islandica and rufa. ...
Present‐day ecology and population structure are the legacies of past climate and habitat perturbations, and this is particularly true for species that are widely distributed at high latitudes. The red knot, Calidris canutus, is an arctic‐breeding, long‐distance migratory shorebird with six recognized subspecies defined by differences in morphology, migration behavior, and annual‐cycle phenology, in a global distribution thought to have arisen just since the Last Glacial Maximum (LGM). We used nextRAD sequencing of 10,881 single‐nucleotide polymorphisms (SNPs) to assess the neutral genetic structure and phylogeographic history of 172 red knots representing all known global breeding populations. Using population genetics approaches, including model‐based scenario‐testing in an approximate Bayesian computation (ABC) framework, we infer that red knots derive from two main lineages that diverged ca. 34,000 years ago, and thus most likely persisted at the LGM in both Palearctic and Nearctic refugia, followed by at least two instances of secondary contact and admixture. Within two Beringian subspecies (C. c. roselaari and rogersi), we detected previously unknown genetic structure among sub‐populations sharing a migratory flyway, reflecting additional complexity in the phylogeographic history of the region. Conversely, we found very weak genetic differentiation between two Nearctic populations (rufa and islandica) with clearly divergent migratory phenotypes and little or no apparent contact throughout the annual cycle. Together, these results suggest that relative gene flow among migratory populations reflects a complex interplay of historical, geographical, and ecological factors.
... The trait is often considered as plastic and changeable over short, decadal time scales (16,17). Current migratory patterns derive from successful adjustments dating back to glacial periods when higher-latitude breeding grounds were unsuitable for breeding (18). During these glacial stages, populations of ...
Significance
We combine tracks of a long-distance migratory bird with high–temporal resolution climate data to reconstruct habitat availability month by month for the past 120,000 y. The seasonal changes of suitable habitat in the past imply that continued seasonal migration was necessary during the glacial maxima. Genomic-based estimates of effective population size indicate that more generally migratory lifestyles can be beneficially adapted to various climatic conditions. Our results provide a major step forward in understanding how migratory species will fare in the future and have important implications for how we understand the role of migration in the distribution of species and potentially speciation.
... There are several biogeographic implications that follow from the discovery of P. leucopus on GMI. This species may have been present on GMI since the Holocene Climatic Optimum, aka the Hypsithermal, a warm period that occurred ~9,000 to 4,000 BP (Pielou 1991). This species is hypothesized to be one member of a suite of species (see Petersen andStewart 2006, Wisheu et al. 1994) that ranged through Maine and southern New Brunswick into Nova Scotia during the hypsithermal period (~6,000-4,000 BP). ...
Grand Manan Island represents the southernmost region of the province of New Brunswick, Canada. Due to its isolation, the island fauna is depauperate, with few native mammal species. Recent molecular genetic analysis of Peromyscus collected from GMI revealed the mitotype (cytochrome b gene) indicative of P. leucopus (White-footed Deermouse). This species previously was known only from mainland Nova Scotia in Maritime Canada. Here we document the occurrence of P. leucopus on Grand Manan Island and discuss the implications of this discovery, most notably as it relates to the endemic P. maniculatus argentatus (Grand Manan Deermouse) and the presence of Lyme disease.
... More recently, this connection was cut off and the St. Joseph River was captured by the Maumee drainage (Graf, 2002;Pielou, 1991), creating a potential route for colonization to the Great Lakes watershed. Several fishes, including a known host for P. clava (Northern Hogsucker, Hypentelium nigricans, Berendzen et al., 2003), and unionids (Threeridge Amblema plicata, Elderkin et al., 2007;Flutedshell suggesting that this geographic region harbors a high amount of unique genetic variation, suggesting long-term persistence and accumulation of genetic diversity. ...
Abstract The shell morphologies of the freshwater mussel species Pleurobema clava (federally endangered) and Pleurobema oviforme (species of concern) are similar, causing considerable taxonomic confusion between the two species over the last 100 years. While P. clava was historically widespread throughout the Ohio River basin and tributaries to the lower Laurentian Great Lakes, P. oviforme was confined to the Tennessee and the upper Cumberland River basins. We used two mitochondrial DNA (mtDNA) genes, 13 novel nuclear DNA microsatellite markers, and shell morphometrics to help resolve this taxonomic confusion. Evidence for a single species was apparent in phylogenetic analyses of each mtDNA gene, revealing monophyletic relationships with minimal differentiation and shared haplotypes. Analyses of microsatellites showed significant genetic structuring, with four main genetic clusters detected, respectively, in the upper Ohio River basin, the lower Ohio River and Great Lakes, and upper Tennessee River basin, and a fourth genetic cluster, which included geographically intermediate populations in the Ohio and Tennessee river basins. While principal components analysis (PCA) of morphometric variables (i.e., length, height, width, and weight) showed significant differences in shell shape, only 3% of the variance in shell shape was explained by nominal species. Using Linear Discriminant and Random Forest (RF) analyses, correct classification rates for the two species' shell forms were 65.5% and 83.2%, respectively. Random Forest classification rates for some populations were higher; for example, for North Fork Holston (HOLS), it was >90%. While nuclear DNA and shell morphology indicate that the HOLS population is strongly differentiated, perhaps indicative of cryptic biodiversity, we consider the presence of a single widespread species the most likely biological scenario for many of the investigated populations based on our mtDNA dataset. However, additional sampling of P. oviforme populations at nuclear loci is needed to corroborate this finding.
... The Puma Lineage probably evolved in North America and then migrated into South America 2-4 MYA during the Great American Interchange after the formation of the Panamanian land bridge (Culver 2010:28). Subsequent phylogenetic analyses have revealed that genetic diversity in the puma is larger in South America in comparison to specimens from North and Central America, which suggests that puma likely had to recolonize North America from South America, following mass extinctions in North America that occurred in the late Pleistocene (Pielou 1991, Culver et al. 2000, Matte et al. 2013. This founder effect is what is believed to have led to the mono-haplotypic character of North American puma identified in several studies via mitochondrial DNA (mtDNA) sequencing (Culver et al. 2000, Caragiulo et al. 2013, Matte et al. 2013. ...
This SSA evaluates the current status of the Florida panther as well as an assessment on the risk of extinction in the future. This SSA applies the conservation biology principles of resiliency, redundancy, and representation (the 3 R’s) to evaluate the current and future condition of the Florida panther. Resiliency, redundancy, and representation are interconnected and overlapping principles that collectively contribute to the viability of a species. We also introduce the concept of a fourth “R,” namely resistance, which describes the willingness of people to accept the species on the landscape. Outdoor recreationalists and rural residents may be concerned about sharing wild spaces with a large carnivore; livestock producers may be concerned about economic losses inflicted by predation; landowners may be concerned about whether regulatory burdens accompany panthers; and citizens in general may be concerned about costs associated with recovery initiatives. The SSA provides a compilation of the best available scientific information on the biological status of the Florida panther but it is not a decisional document (does not include any recommendations or decisions regarding the status of the listed entity). The SSA is, however, a stand-alone, science-focused assessment for use in policy-guided decisions under the ESA and to inform future Florida panther conservation and management efforts.
... The Puma Lineage probably evolved in North America and then migrated into South America 2-4 MYA during the Great American Interchange after the formation of the Panamanian land bridge (Culver 2010:28). Subsequent phylogenetic analyses have revealed that genetic diversity in the puma is larger in South America in comparison to specimens from North and Central America, which suggests that puma likely had to recolonize North America from South America, following mass extinctions in North America that occurred in the late Pleistocene (Pielou 1991, Culver et al. 2000, Matte et al. 2013. This founder effect is what is believed to have led to the mono-haplotypic character of North American puma identified in several studies via mitochondrial DNA (mtDNA) sequencing (Culver et al. 2000, Caragiulo et al. 2013, Matte et al. 2013. ...
This report evaluates the current status of the Florida panther as well as an assessment on the risk of extinction in the future. This SSA applies the conservation biology principles of resiliency, redundancy, and representation (the 3 R's) to evaluate the current and future condition of the Florida panther. Also assessed is the concept of a fourth "R," namely resistance, which describes the willingness of people to accept the species on the landscape. The SSA provides a compilation of the best available scientific information on the biological status of the Florida panther, but it is not a decisional document. The SSA is a stand-alone, science-focused assessment for use in policy-guided decisions under the U.S. Endangered Species Act and to inform future Florida panther conservation and management efforts.
... The hypotheses of sudden demographic expansion or spatial expansion of the populations cannot be rejected, perhaps with the exception for MCA D-loop.Analyses reveal that assumption of constant population size or no selection is violated and there are signs and signatures of population expansion. Signatures of demographic and spatial expansion are commonly detected in many organisms inhabiting temperate zones and is mainly attributed to the recolonizations of areas freed by the retreat of ice sheets after major glaciation events(Pielou 1991;Hewitt 2000). Numerous studies have detected signatures of postglacial expansion of populations in mammals(Galbreath and Cook 2004;Lessa et al. 2003;Korsten et al. 2009;Wójcik et al. 2010), birds(Boulet and Gibbs 2006;Qu et al. 2010;Pulgarín-R et al. 2012), reptiles (Guiher and Burbrink 2008), and plants(Hwang et al. 2003;Hoarau et al. 2007;Gao et al. 2015).Phylogeographic studies of Apodemus have also noted signatures of demographic expansions indicating post-glacial recolonizations(Michaux et al 2005;Sakka et al. 2010;Fan et al. 2012;Suzuki et al. 2015).Apodemus gurkha are currently distributed at an elevational range between 2200 m and 3600 m. ...
Late Miocene, 8 to 6 million years ago (Ma), climatic changes brought about dramatic floral and faunal changes. Cooler and drier climates that prevailed in the Late Miocene led to expansion of grasslands and retreat of forests at a global scale. Palaeogeographic studies suggest a global vegetation change causing an abrupt increase in C4 plant biomass while C3 biomass decreased between 8 and 6 Ma. Subsequent cycles of cooler and drier climatic conditions during the Mid-Pliocene (3.5–3 Ma) and Pleistocene (2.8–2.5; 1.8–1.6; 1.0–0.8 Ma) also caused forests to retreat into isolated refugia which played an important role in events that led speciation and radiation of Muroid (Order Rodentia, Superfamily Muroidea) rodents. Muroid rodents are comprised of 6 families (Placanthomyidae, Spalacidae, Calomyscidae, Nesomyidae, Cricetidae, and Muridae) and make up close to one-third of named mammal species. Family Cricetidae and Muridae are especially speciose (containing ~1600 species altogether) and much of the diversity within these families arose during or after the Late Miocene. My dissertation deals with the systematics and historical biogeography of these fast-evolving groups of rodents with an emphasis on the genera Apodemus and Hybomys (Subfamily Murinae, Family Muridae), and Neodon (Subfamily Arvicolinae, Family Cricetidae). Habitat specialists such as Apodemus that occupy broadleaf forests, and Hybomys that occupy rainforests were likely isolated in forest refugia after the retreat of forests facilitating allopatric speciation. While voles in the subfamily Arvicolinae, that are associated with grasslands, expanded their range when forests retreated and speciated when grasslands retreated. In addition, field work carried out for this project in Nepal included several localities previously not sampled for small mammals. Most of Nepal is poorly surveyed and the first chapter focuses on the history of mammalogical surveys in Nepal and adds new localities for small mammal species, expanding the known range of the Nepalese endemic Himalayan wood mouse (Apodemus gurkha).
... The Salish Sea is a semi-enclosed system bounded by Vancouver Island, and connected to the Pacific Ocean through the Juan de Fuca Strait in the south and narrow channels to the north (Figure 2). The topographic complexity and glacial history of BC's coastline, that likely influence species distributions (Pielou, 1991), creates unique challenges for modeling and as a result nearshore connectivity is poorly understood. In this region, there are also two important climatic changes that drive strong seasonal differences in hydrodynamics and have ecological relevance: (1) the spring transition between Aleutian Low and North Pacific High pressure dominance over the northeast Pacific that suppresses winter storm activity resulting in phytoplankton blooms (Kathleen Collins et al., 2009;Bakri and Jackson, 2019), and (2) the summer freshet, dominated by the undammed Fraser River that increases the stratification and reduces the residence time of the surface layer (Pawlowicz et al., 2007). ...
The dispersal of marine organisms is a critical process for the maintenance of biodiversity and ecosystem functioning across a seascape. Understanding the patterns of habitat connectivity that arise from the movement of multiple species can highlight the role of regional processes in maintaining local community structure. However, quantifying the probability and scale of dispersal for marine organisms remains a challenge. Here, we use a biophysical model to simulate dispersal, and we conduct a network analysis to predict connectivity patterns across scales for the community of invertebrates associated with seagrass habitat in British Columbia, Canada. We found many possible connections and few isolated habitat meadows, but the probability of most connections was low. Most habitat connections occurred within 3 days of dispersal time over short distances, indicating potential limits to long distance dispersal and little effect of species-specific dispersal abilities on the potential spatial extent of habitat connectivity. We then highlight the different roles that individual seagrass meadows can play in maintaining network connectivity. We also identify clusters of connected meadows and use these clusters to estimate the spatial scale of community dynamics. The connectivity patterns generated by our dispersal simulations highlight the importance of considering marine communities in their broad seascape context, with applications for the prioritization and conservation of habitat that maintains connectivity.
... Species range distributions shift over evolutionary timescales, both expanding and contracting within the cyclical nature of glaciations and periods of warmth (Pielou, 1991). Given that we are seeing a rapid increase in global temperatures, we might expect species ranges to shift accordingly at a much faster rate than has been observed in the past; this will be even more challenging for species living in mountainous regions, such as the Pacific Northwest (PNW) of the United States (Dobrowski & Parks, 2016). ...
Aim
Given that salamanders have experienced large shifts in their distributions over time, we determined how each species of Plethodon in the Pacific Northwest would respond to climate change. We incorporated several greenhouse scenarios both on a species-by-species basis, and also using phylogenetic groups, with the aim to determine the best course of action in managing land area to conserve diversity in this group.
Location
Pacific Northwest of the United States (northern CA, OR, WA, ID, and MT).
Major taxa studied
Western Plethodon salamanders.
Methods
Species distribution models were estimated using MaxEnt for the current time period and for several future climate scenarios using bioclimatic data layers. We used several methods to quantify the change in habitat suitability over time from the models. We explored aspects of the climate layers to determine whether we can expect a concerted response to climate change due to similarity in ecological niche or independent responses that could be harder to manage.
Results
The distribution of western Plethodon salamander species is strongly influenced by precipitation and less so by temperature. Species responses to climate change resulted in both increases and decreases in predicted suitable habitat, though most species ranges do not contract, especially when taken as a phylogenetic group.
Main conclusions
While some established habitats may become more or less climatically suitable, the overall distribution of species in this group is unlikely to be significantly affected. Clades of Plethodon species are unlikely to be in danger of extirpation despite the possibility that individual species may be threatened as a result of limited distributions. Grouping species into lineages with similar geographic ranges can be a viable method of determining conservation needs. More biotic and dispersal information is needed to determine the true impact that changes in climate will have on the distribution of Plethodon species.
... The current distribution of A. k. occidentalis spans both unglaciated and glaciated regions of the NRM [the Last Glacial Period occurred from ~115 000-11 700 years ago (Pielou, 1991)], and our data suggest that both historical isolation (e.g. the deep split between the Clearwater clade and all remaining clades) and more recent expansions (e.g. the NE clade) have shaped the spatial distribution and genetic structure of this species. Genetic diversity is structured at both deep and shallow scales, with there being several deeply divergent mtDNA lineages that, in turn, exhibit shallower coalescent events among samples. ...
The Northern Rocky Mountain ecosystem supports rich biological diversity with many endemic and rare species. Extant endemics display two biogeographic patterns: widespread species with fragmented populations, and narrow-range endemics. These distributions are shown by the congeneric snails Anguispira kochi occidentalis and Anguispira nimapuna. These two taxa are disjunct from the remaining species of the genus, which achieves its greatest diversity in eastern North America. Given the disjunct nature of A. k. occidentalis and A. nimapuna, we here present a mtDNA phylogeny of the genus that includes both eastern and western species to assess the phylogenetic position of A. k. occidentalis and A. nimapuna. We then reconstruct the demographic history of A. k. occidentalis and A. nimapuna by analysing current patterns of genetic variation and interpreting the results considering the historical biogeography of the region. Both A. k. occidentalis and A. nimapuna represent unique taxa that are genetically and geographically distinct from their congeners. The current distribution and genetic structure of A. k. occidentalis has been shaped by both historical isolation in refugia and more recent northward shifts, whereas A. nimapuna is represented by two populations with shallow divergence in an area of long-term habitat stability.
... At the cross-roads of the northern continents, repeated exposure of the Bering Isthmus (often referred to as the Bering Land Bridge) during glacial (cold) climate phases, as a result of terrestrial ice accumulation and corresponding lowered sea-levels, allowed for communities to continuously ebb and flow through this region (Sher 1999;Repenning 2001;Hoberg et al. 2012). Although ice sheets covered much of Europe and North America, displacing species during glacial times, vast areas within Beringia and central Asia remained icefree, supporting predominantly arid polar steppe communities during glacial periods and mesic tundra or boreal forest biomes during interglacial (warm) stages, including at present (Pielou 1991;Elias et al. 1996;Guthrie 2001;Abbott and Brochmann 2003;Hewitt 2004;Haukisalmi et al. 2006). As such, species could periodically disperse between continents, generating Holarctic linkages (Hopkins 1959;Waltari et al. 2007;Eidesen et al. 2013). ...
We synthesize the historical biogeography of non-marine fauna (mammals, birds, fish, non-parasitic and parasitic invertebrates) occurring across Bering Sea islands, considering endemism, species with origins in both North America and Far East Asia, and the impacts of introduced species through the Bering region. Insular communities often constitute assemblages of unique evolutionary lineages that reflect both neutral and selective processes of diversification as a consequence of isolation and through responses to in situ environmental change. However, current knowledge of the basic distribution, ecology, and evolutionary identity of the majority of terrestrial species through the Bering Sea region is still generally lacking. A preponderance of scientific effort associated with these islands has instead focused on conservation and management of marine-associated species and economically viable biological resources. Given the critical role that terrestrial environments play in maintaining evolutionary and ecological linkages between land and sea, a greater understanding of existing biodiversity, and the biological processes that influence community integrity through this remote region is warranted. Resolving responses of resident insular species to rapidly warming Arctic climate and to modern human-associated disturbances provides valuable insight for effective management of future population trajectories and for revealing the dynamics of intra- and inter-specific connectivity across the northern hemisphere and between marine and terrestrial ecosystems. The location of this region at a high-latitude cross-roads has led to a preponderance of island taxa having trans-Beringian distributions. Species associated with the Palearctic or the Nearctic occur across a strong longitudinal gradient, reflecting the role of the Bering Sea as a dispersal filter between mainland areas. Aleutian oceanic islands reflect different biogeographic histories among taxonomic groups from land-bridge islands of the Bering Sea. We discuss evidence of recent biodiversity responses to modern environmental perturbations, including continued colonisations and novel species interactions, and call for increased scientific scrutiny of terrestrial fauna across these remote outposts.
... During glacial advances in North America in the late Pleistocene, terrestrial species were primarily isolated south of the major ice sheets or in the highlatitude Beringian refugium (Hultén, 1937). Multiple smaller refugia are also hypothesized in far northern Canada (Fedorov & Stenseth, 2002), in dispersed mountain nunataks (Pielou, 1992), and along the North Pacific Coast (NPC) within southeast Alaska's Alexander Archipelago (e.g., Baranof, Chichagof, Dall, Heceta, and Prince of Wales islands; Carrara et al., 2003;Carrara et al., 2007;Ager, 2019), British Columbia's Haida Gwaii Archipelago, and the surrounding coastline (Foster, 1965;Heusser, 1989;Mathewes & Clague, 2017). ...
Aim
Numerous glacial refugia have been hypothesized along North America's North Pacific Coast that may have increased divergence of refugial taxa, leading to elevated endemism and subsequently clustered hybrid zones following deglaciation. The locations and community composition of these ice‐free areas remains controversial, but whole‐genome sequences now enable detailed analysis of the demographic and evolutionary histories of refugial taxa. Here, we use genomic data to test spatial and temporal processes of diversification among martens with respect to the Coastal Refugium Hypothesis, to understand the role of climate cycling in shaping diversity across complex landscapes.
Location
North America and North Pacific Coast archipelagos.
Taxon
North American martens (Martes).
Methods
Short‐read whole‐genome resequencing data were generated for 11 martens: four M. americana, four M. caurina, two hybrids, and one outgroup (Martes zibellina). Sampling was representative of known genetic clades within New World martens, including sampling within insular and continental hybrid zones and along the North Pacific Coast (five island populations). ADMIXTURE, F‐statistics, and D‐statistics (ABBA‐BABA) were used to identify introgression and infer directionality. Heterozygosity densities, estimated via PSMC, were used to characterize historical demography at and below the species level to infer refugial and colonization processes.
Results
Forest‐associated Pacific martens (M. caurina) are divided into distinct insular and continental clades consistent with the Coastal Refugium Hypothesis. There was no evidence of introgression on islands that received historical translocations of American pine martens (M. americana), but introgression was detected in two active zones of secondary contact: one insular and one continental. Only early‐generational hybrids were identified across multiple hybrid zones, a pattern consistent with potential genetic swamping of M. caurina by M. americana.
Main conclusions
Despite an incomplete fossil record, genomic evidence supports the persistence of forest‐associated martens, likely the insular Pacific marten lineage, along the western edges of the Alexander Archipelago during the Last Glacial Maximum. This discovery informs our understanding of refugial paleoenvironments, critical to interpreting refugial timing, duration, and community composition. Genomic reevaluations of other taxa along North America's North Pacific Coast may yield new and deeper perspectives on the history of refugial forest communities and the role of dynamic climate shifts in shaping high‐latitude diversity across complex insular landscapes.
... The recent physiographic history of the Gulf Coast drainages is dynamic. Northern, interior drainages were repeatedly glaciated as recently as 10,000 years ago while lowland, coastal streams were repeatedly inundated and reconnected by rising and falling sea levels, respectively (Anderson et al., 2004;Galloway et al., 2011;Haq et al., 1987;Pielou, 2008;Riggs, 1984). ...
Aim
Freshwater mussels share habitat and are parasites of freshwater fishes during the larval life stage. Therefore, models of fish biogeography may also explain the historical biogeography of freshwater mussels. We tested this assumption using predictions of three biogeographic models constructed for northern Gulf of Mexico drainages on a freshwater mussel species complex. Specifically, we tested (1) if speciation was due to vicariant events of fluctuating sea levels that separated lineages east‐west of the Mobile Basin (Central Gulf Coast speciation hypothesis), (2) if the timing of divergences occurred 8.5–3.5 MYA (Gulf Coast allopatric speciation model) and (3) if diversification in Mississippi River populations was recent and for evidence of population increase consistent with range expansion into northern deglaciated regions (Pleistocene glaciation model).
Location
Eastern North America.
Taxon
Freshwater mussels (Bivalvia: Unionidae), Lampsilis teres and L. floridensis.
Methods
We collected 249 specimens from 73 localities across the group's distribution. We used three molecular markers (COI, NDI & ITSI) to conduct time calibrated Bayesian phylogenetic analyses, phylogeographic analyses (AMOVA & SAMOVA) and demographic analyses including Bayesian skyline plots.
Results
Lampsilis teres and L. floridensis are allopatric species whose distributions meet at the eastern edge of the Mobile Basin. Speciation was estimated to occur in the late Miocene. Populations from isolated river systems surrounding the Gulf of Mexico are almost all monophyletic. Mississippi drainage samples formed a shallow clade with recent diversification and showed evidence of recent population expansion.
Main conclusions
The historical biogeography of the L. teres species complex is broadly consistent with tested ichthyofaunal models. The timing of speciation and intraspecific divergences correspond to low sea‐level events suggesting that Gulf Coast sea‐level fluctuations are responsible for dispersal (sea‐level recession) and subsequent cladogenesis (sea‐level inundation). Consistent with numerous other freshwater studies, we found the Mobile Basin to be a suture zone, which may be due to the narrow, offshore continental shelf.
... Postglacial lakes are often viewed as ideal systems to study adaptive processes such as the origins and maintenance of resource polymorphism (e.g., Schluter, 1996;Snorrason & Skúlason, 2004) due to relatively low species diversity and productivity, and frequent high habitat segregation between littoral and pelagic morphs (e.g., Klemetsen, 2010;Pielou, 2008). In postglacial lakes, colonization and adaptation have occurred relatively recently, as recent as 10,000 years ago (e.g., . ...
Polymorphism facilitates coexistence of divergent morphs (e.g., phenotypes) of the same species by minimizing intraspecific competition, especially when resources are limiting. Arctic char (Salvelinus sp.) are a Holarctic fish often forming morphologically, and sometimes genetically, divergent morphs. In this study, we assessed the morphological and genetic diversity and divergence of 263 individuals from seven populations of arctic char with varying length‐frequency distributions across two distinct groups of lakes in northern Alaska. Despite close geographic proximity, each lake group occurs on landscapes with different glacial ages and surface water connectivity, and thus was likely colonized by fishes at different times. Across lakes, a continuum of physical (e.g., lake area, maximum depth) and biological characteristics (e.g., primary productivity, fish density) exists, likely contributing to characteristics of present‐day char populations. Although some lakes exhibit bimodal size distributions, using model‐based clustering of morphometric traits corrected for allometry, we did not detect morphological differences within and across char populations. Genomic analyses using 15,934 SNPs obtained from genotyping by sequencing demonstrated differences among lake groups related to historical biogeography, but within lake groups and within individual lakes, genetic differentiation was not related to total body length. We used PERMANOVA to identify environmental and biological factors related to observed char size structure. Significant predictors included water transparency (i.e., a primary productivity proxy), char density (fish·ha‐1), and lake group. Larger char occurred in lakes with greater primary production and lower char densities, suggesting less intraspecific competition and resource limitation. Thus, char populations in more productive and connected lakes may prove more stable to environmental changes, relative to food‐limited and closed lakes, if lake productivity increases concomitantly. Our findings provide some of the first descriptions of genomic characteristics of char populations in arctic Alaska, and offer important consideration for the persistence of these populations for subsistence and conservation.
... Like many North American boreal freshwater species, the spatial genetic structure of the lake charr was profoundly shaped by Pleistocene glaciations (Bernatchez and Wilson 1998;Wilson and Mandrak 2021). Repeated glacial advances and retreats alternated between destroying and revealing suitable habitats and, when combined with dispersal largely restricted to freshwater habitats, impacts on species' ecology and genomes have been especially pronounced (Pielou 1991;Wilson and Mandrak 2021). In a comprehensive project to reveal historical biogeographic origins and patterns of re-distribution of the lake charr, Hebert (1996, 1998) tested alternate dispersal hypotheses using restriction fragment length polymorphism (RFLP) analysis of mitochondrial DNA (mtDNA). ...
The use of genetic information in fishery management has become increasingly valuable as input to decision making. The lake charr Salvelinus namaycush represents an important model species of management concern for studying ecological divergence. We compiled a comprehensive assessment of the knowledge of lake charr genetic diversity. The following topics were reviewed: spatial patterns of genetic diversity, the relationship between genetic and morphological distinctiveness of ecotypes, heritability of phenotypes, evidence for “reverse speciation,” and genetic effects of hatchery stocking. Important patterns that emerged were: strong divergence and high genetic uniqueness for most inland lake populations; evidence for heritability of traits associated with lake charr ecotypes; inconsistent support for genetic differentiation of ecotypes; an emerging view that lake charr diversity is distributed along a depth gradient in large lakes rather than discrete ecotypes; and hatchery supplementation and stocking have had profound but highly variable impacts on genetic diversity of populations. Knowledge gaps were identified to guide future research and to assist lake charr management and include investigations into the molecular mechanisms and evolutionary processes generating phenotypic diversity.
... Extended isolation in glacial refugia is a documented driver of diversification worldwide (Bennett & Provan, 2008;Hewitt, 1996;Stewart et al., 2010). The cyclic expansion and contraction of glaciers through the Quaternary (2.6 Mya-present) is credited with structuring flora and fauna at the high latitudes (Pielou, 2008), whereby episodes of allopatric refugial isolation lead to genetic and morphological differentiation over time (e.g. mammals, Heaton et al., 1996, Sawyer et al., 2019plants, DeChaine et al., 2014;insects, Ujvárosi et al., 2010). ...
Aim
Refugial isolation during glaciation is an established driver of speciation; however, the opposing role of interglacial population expansion, secondary contact, and gene flow on the diversification process remains less understood. The consequences of glacial cycling on diversity are complex and especially so for archipelago species, which experience dramatic fluctuations in connectivity in response to both lower sea levels during glacial events and increased fragmentation during glacial recession. We test whether extended refugial isolation has led to the divergence of genetically and morphologically distinct species within Holarctic ermine (Mustela erminea), a small cosmopolitan carnivore species that harbours 34 extant subspecies, 14 of which are insular endemics.
Location
Holarctic.
Methods
We use genetic sequences (complete mitochondrial genomes, four nuclear genes) from >100 ermine (stoats) and geometric morphometric data for >200 individuals (27 of the 34 extant subspecies) from across their Holarctic range to provide an integrative perspective on diversification and endemism across this complex landscape. Multiple species delimitation methods (iBPP, bPTP) assessed congruence between morphometric and genetic data.
Results
Our results support the recognition of at least three species within the M. erminea complex, coincident with three of four genetic clades, tied to diversification in separate glacial refugia. We found substantial geographic variation within each species, with geometric morphometric results largely consistent with historical infraspecific taxonomy.
Main conclusions
Phylogeographic structure mirrors patterns of diversification in other Holarctic species, with a major Nearctic‐Palearctic split, but with greater intraspecific morphological diversity. Recognition of insular endemic species M. haidarum is consistent with a deep history of refugial persistence and highlights the urgency of mindful management of island populations along North America's North Pacific Coast. Significant environmental modification (e.g. industrial‐scale logging, mining) has been proposed for a number of these islands, which may elevate the risk of extinction of insular palaeoendemics.
... Many of them present intraspecific phenotypic and genetic variation across their distribution ranges that are the basis of subspecies and species splits. As a consequence of the strong climatic seasonality in the Arctic, with only a few months of suitable temperatures but very high productivity (Pielou, 1991), shorebirds, as well as other species, are forced to migrate. Most Arctic shorebird species arrive at the breeding grounds in late June and stay between June and early August, migrating back to the non-breeding grounds in temperate to tropical latitudes in August-September (Meltofte et al., 2007), being some of the animal groups with the longest migrations on Earth. ...
Aim
Spatio‐temporal changes have likely caused range fragmentation and population isolation, which could have given rise to the observed current intraspecific differentiation in some species. Here, we test several hypotheses on the potential effect of Pleistocene glacial cycles in the diversification of Arctic shorebird species, comparing between different scenarios of fragmentation of the breeding distribution during glacial and interglacial periods.
Location
Global.
Taxon
Arctic migratory shorebirds.
Methods
We performed species distribution models (SDMs) to explore the changes in the breeding and non‐breeding ranges of 69 species between the last glacial maximum ( c . 21,000 years ago) and the present. We also included independent evidence from the fossil record and estimations on the potential extension of the tundra during glacial periods to validate the results from the SDMs. We assigned each species to one of four potential scenarios based on fragmentation and potential recolonization patterns of their breeding ranges during glaciations.
Results
Our findings show that most of the species with subspecies experienced fragmentation of their ranges during the glacial, the interglacial or both periods. Meanwhile, the majority of the monotypic species maintained their ranges as a continuum. Moreover, the impacts of glacial cycles in the distribution were not homogeneous across the Arctic, and some regions were more prone to the fragmentation of breeding ranges than others.
Main conclusions
Our work suggests that Pleistocene climatic cycles drove the diversification of Arctic shorebirds by creating allopatric breeding distributions. While the fragmentation of the breeding ranges occurred mainly during glacial periods, interglacials also played a part in maintaining or establishing newly isolated breeding populations for many species. Furthermore, species' distribution changes varied between different regions and habitats, which determined current shorebird diversity patterns.
... The phylogeography of mammals in the Great Lakes region is of particular interest with respect to understanding range changes, in part because the lakes serve as substantial water barriers that can severely limit the redistribution of terrestrial species (Rowe et al. 2006;Taylor and Hoffman 2010). Also, the region is relatively young, having been ice-free for only about 10,000 to 12,000 years (Pielou 1991;Holman 2001), which is recent enough that some species still show genetic signatures of their postglacial migrations (Rowe et al. 2004(Rowe et al. , 2006Taylor and Hoffman 2010). The region also encompasses a historical dividing line between two substantially different mammalian faunal assemblages (Baker 1983;Kurta 2017) associated with two different forest types, eastern deciduous forest across the southern part of the lakes and mixed deciduous-boreal forest to the north. ...
Many organisms worldwide are responding to rapid climate change by shifting their geographic ranges. The white-footed mouse, Peromyscus leucopus, has expanded its range northward in Michigan and Wisconsin since 1980 and is now common in localities where it was previously unknown. To investigate the origin and history of the newly established populations, complete D-loop sequences were analyzed from 595 white-footed mice collected throughout the northern Great Lakes region. Mice from Wisconsin and the western Upper Peninsula (UP) of Michigan make up a well-differentiated lineage, while the eastern UP and the Lower Peninsula (LP) of Michigan form a second lineage. The two lineages diverged about 34,000 BP, well before they migrated to the Great Lakes region. The close genetic relationship between mice in the LP and those in the eastern UP is probably due primarily to accidental transport by humans and may have implications for the spread of Lyme disease in the Upper Midwest.
... During the Pleistocene glacial cycles, most of the PNW was subjected to repeated glaciation. Only the northernmost portions of the Cascades Range were affected, with montane glaciers in the Cascades probably pushing forest habitats to lower altitudes, and ice sheets covering a significant portion of the northern Rocky Mountains (Pielou, 1991;Delcourt & Delcourt, 1993). Nevertheless, the inland rainforest ecosystem contains a collection of pre-Pleistocene endemic species (i.e. ...
The history of the currently disjunct temperate rainforests of the Pacific Northwest of North America has shaped the evolution and diversity of endemics. This study focuses on how geological and climatic perturbations have driven speciation in the area by isolating lineages. We investigated the phylogenetic relationships and historical biogeography of the endemic jumping slugs (genus Hemphillia) using a multi-locus phylogeny. We evaluated the spatial distribution and divergence times of major lineages, generated ancestral area probabilities and inferred the biogeographical history of the genus. Our study revealed eight genetic lineages that formed three clades: one clade consisting of two Coast/Cascade lineages, and two reciprocally monophyletic clades that each contain a Coast/Cascade and two Rocky Mountains taxa. The results of the biogeographical analysis suggest that the ancestral range of the genus occupied Coast/Cascade habitats and then spread across into Northern Rocky Mountain interior habitats with subsequent fragmentations isolating coastal and inland lineages. Finally, there have been more recent speciation events among three lineage pairs that have shaped shallow structures of all clades. We add to our knowledge of the biogeographical history of the region in that we discovered diversification and speciation events that have occurred in ways more complex than previously thought.
... This period (named "El Abra" in the northern Andes, Younger Dryas or Dryas III in Scandinavia and northern Europe, 11 800-9 600 years ago (Clapperton, 1993), or central European Tardi-glacial (Dollfus, 1964)) was crucial in the extinction of mammals. Indeed, 80% of large mammal species (around 40 species) were eliminated from North America (Martin, 1989;Pielou, 1991). ...
The species within Xenarthra (sloths, anteaters, and armadillos) are quintessential South American mammals. Of the three groups, Vermilingua (anteaters) contains the fewest extant and paleontological species. Here, we sampled and sequenced the entire mitochondrial genomes (mitogenomes) of two Tamandua species (Tamandua tetradactyla and Tamandua mexicana) (n=74) from Central and South America, as well as Myrmecophaga tridactyla (n=41) from South America. Within Tamandua, we detected three different haplogroups. The oldest (THI) contained many specimens with the T. tetradactyla morphotype (but also several with the T. mexicana morphotype) and originated in southeastern South America (currently Uruguay) before moving towards northern South America, where the THII haplogroup originated. THII primarily contained specimens with the T. mexicana morphotype (but also several with the T. tetradactyla morphotype) and was distributed in Central America, Colombia, and Ecuador. THI and THII yielded a genetic distance of 4%. THII originated in either northern South America or "in situ" in Central America with haplogroup THIII, which consisted of ~50% T. mexicana and 50% T. tetradactyla phenotypes. THIII was mostly located in the same areas as THII, i.e., Central America, Ecuador, and Colombia, though mainly in the latter. The three haplogroups overlapped in Colombia and Ecuador. Thus, T. tetradactyla and T. mexicana were not reciprocally monophyletic. For this reason, we considered that a unique species of Tamandua likely exists, i.e., T. tetradactyla. In contrast to Tamandua, M. tridactyla did not show different morphotypes throughout its geographical range in the Neotropics. However, two very divergent genetic haplogroups (MHI and MHII), with a genetic distance of ~10%, were detected. The basal haplogroup, MHI, originated in northwestern South America, whereas the more geographically derived haplogroup, MHII, overlapped with MHI, but also expanded into central and southern South America. Thus, Tamandua migrated from south to north whereas Myrmecophaga migrated from north to south. Our results also showed that temporal mitochondrial diversification for Tamandua began during the Late Pliocene and Upper Pleistocene, but for Myrmecophaga began during the Late Miocene. Furthermore, both taxa showed elevated levels of mitochondrial genetic diversity. Tamandua showed more evidence of female population expansion than Myrmecophaga. Tamandua experienced population expansion ~0.6-0.17 million years ago (Mya), whereas Myrmecophaga showed possible population expansion ~0.3-0.2 Mya. However, both taxa experienced a conspicuous female decline in the last 10 000-20 000 years. Our results also showed little spatial genetic structure for both taxa. However, several analyses revealed higher spatial structure in Tamandua than in Myrmecophaga. Therefore, Tamandua and Myrmecophaga were not subjected to the same biogeographical, geological, or climatological events in shaping their genetic structures.
... Contemporary patterns of genetic differentiation among striped bass populations result from the natural history of the species. Pleistocene glaciation [49] affected the genetic structure of fish populations along the Atlantic Coast, creating population genetic differentiation between refuge populations in the south and populations further north founded by later recolonization events [50][51][52]. Southeastern U.S. striped bass populations have a relatively high level of genetic differentiation because of their long history, small effective population sizes, and some degree of isolation. ...
Striped bass is the subject of important commercial and sport fisheries in North America. The Roanoke River drainage—especially Smith Mountain Lake, Leesville Lake, and Kerr Reservoir—has popular recreational striped bass fisheries. After construction of five hydroelectric dams, populations became landlocked, declined, and have been supplemented by stocking. A key basis for responsibly augmenting populations is to characterize genetic variation and incorporate the findings into responsible hatchery and stocking practices. Genetic variation at 12 microsatellite DNA loci was evaluated among 837 striped bass representing 16 collections across the native range; populations from rivers in South Carolina, North Carolina, Chesapeake Bay, and Hudson River were screened to provide context for assessing genetic structure within the Roanoke system. Analysis of population genetic differentiation showed landlocked Roanoke River striped bass to be distinctive. Subject to genetic isolation, high M ratios, and relatively low Ne estimates suggest loss of genetic variation, and relatedness analysis showed heightened frequencies of related individuals. These insights into population genetics, demographics, and existing guidelines for broodstock acquisition and mating designs can inform genetically cognizant hatchery management and stocking for striped bass in the Roanoke River drainage. In particular, we recommend the use of larger numbers of breeders and factorial mating designs to increase the genetic diversity of propagated striped bass stocked within the Roanoke River drainage.
... Through the Pleistocene (2.6 million -10,000 years ago), central Beringia experienced multiple cycles of exposure and inundation from sea level changes driven by glacial cycles, causing intermittent periods of terrestrial connectivity between Eurasia and North America, followed by isolation (Figure 1; Hopkins, 1959;Hopkins, McNeil, Merklin, & Petrov, 1965). This episodic cycling, estimated to have occurred at least nine and possibly up to twenty times or more during the Pleistocene (Hopkins, 1967;Pielou, 2008), repeatedly connected and disconnected the biota of Eurasia and North America. This natural, long-term experiment could cause varying estimates of timing and degrees of divergence between populations occurring on both sides of Beringia (trans-Beringian taxa), because different population pairs will likely have split during different flooding events throughout the past 2.6 million years. ...
Determining how genetic diversity is structured between populations that span the divergence continuum from populations to biological species is key to understanding the generation and maintenance of biodiversity. We investigated genetic divergence and gene flow in eight lineages of birds with a trans‐Beringian distribution, where Asian and North American populations have likely been split and reunited through multiple Pleistocene glacial cycles. Our study transects the speciation process, including eight pairwise comparisons in three orders (ducks, shorebirds, and passerines) at population, subspecies, and species levels. Using ultraconserved elements (UCEs), we found that these lineages represent conditions from slightly differentiated populations to full biological species. Although allopatric speciation is considered the predominant mode of divergence in birds, all of our best divergence models included gene flow, supporting speciation with gene flow as the predominant mode in Beringia. In our eight lineages, three were best described by a split‐migration model (divergence with gene flow), three best fit a secondary‐contact scenario (isolation followed by gene flow), and two showed support for both models. The lineages were not evenly distributed across a divergence space defined by gene flow (M) and differentiation (FST), instead forming two discontinuous groups: one with relatively shallow divergence, no fixed SNPs, and high rates of gene flow between populations; and the second with relatively deeply divergent lineages, multiple fixed SNPs, and low gene flow. Our results highlight the important role that gene flow plays in avian divergence in Beringia.
... As the world's 136 ninth largest and 19 th deepest lake, the lake has a complex, multi-armed surface area of 31,790 137 km 2 and a maximum depth of 446 m (mean depth = 90 m). Great Bear Lake was formed by 138 scouring from the Laurentide ice-sheet during the Pleistocene and was originally part of glacial 139 Lake McConnell 8,000-10,000 yr BP (Johnson, 1975;Pielou, 2008). The lake has 140 characteristics typical of an arctic lake: ultra-oligotrophic, short ice-free season, and a simple 141 food web supporting only 15 fish species (Alfonso, 2004;Johnson, 1975;MacDonald et al., 142 2004). ...
... It has been estimated that up to 20 glaciation events occurred in the Pleistocene, with glacial periods spanning approximately 100,000 years and interglacial periods lasting 10,000 to 12,000 years (Dawson, 1992). Freshwater habitats were altered through the destruction of old systems and the creation of new lakes and rivers (Pielou, 1991). In some regions, large proglacial lakes formed during deglaciation events, allowing the dispersal of freshwater species (Dyke & Prest, 1987). ...
In the present study we evaluate the population structure and potential colonization routes of the silverside Chirostoma humboldtianum through approximate Bayesian computations. Six microsatellite loci were amplified in a total of 288 individuals from six different locations covering the complete geographic distribution of the species. Additionally, two mitochondrial DNA markers, a D loop control region and cytochrome b were amplified in a subset of 107 individuals. The results found with microsatellites allow recovering well‐structured populations that have experienced a drastic reduction in the effective population size. On the other hand, mtDNA sequences showed a moderate phylogeographic structure with shared haplotypes between geographic localities and signalsof a slight increase in the effective population size. Finally, the approximate Bayesian computation analysis performed with both datasets suggested a west‐to‐east colonization route for the species in Central Mexico.
... New England can serve to illustrate the uncertainties observed for the range of A. americanum. The Pleistocene glaciations clearly affected species distribution and demography in North America (Hewitt, 2000;Prentice, Bartlein, & Webb, 1991;Sakamoto, Goddard, & Rasgon, 2014), and many species are assumed to have expanded their range northwards following the retreat of the most recent glaciers (~10,000 years ago) (Cox, Stringer, Moseley, Chippindale, & Streicher, 2018;Pielou, 1991). Amblyomma americanum could be one of those species. ...
Range expansions are a potential outcome of changes in habitat suitability, which commonly result as a consequence of climate change. Hypotheses on such changes in the geographic distribution of a certain species can be evaluated using population genetic structure and demography. In this study we explore the population genetic structure, genetic variability, demographic history of, and habitat suitability for Amblyomma americanum, a North American tick species that is a known vector of several pathogenic microorganisms. We used a double digestion restriction site‐associated DNA sequencing technique (dd‐RAD seq) and discovered 8,181 independent single nucleotide polymorphisms (SNPs) in 189 ticks from across the geographic range of the species. Genetic diversity was low, particularly when considering the broad geographic range of this species. The edge populations were less diverse than populations belonging to the historic range, possibly indicative of a range expansion, but this hypothesis was not statistically supported by a test based on genetic data. Nonetheless, moderate levels of population structure and substructure were detected between geographic regions. For New England, demographic and species distribution models support a scenario where A. americanum was present in more northern locations in the past, underwent a bottleneck, and subsequently recovered. These results are consistent with a hypothesis that this species is re‐establishing in this area, rather than one focused on range expansion from the south. This hypothesis is consistent with old records describing the presence of A. americanum in the northeastern US in the early colonial period.
This report is the first to identify the presence of the extinct ground sloth Glossotherium tropicorum from Pleistocene-aged tar pit deposits in Trinidad. G. tropicorum is known primarily from extensive skeletal material recovered from the Pleistocene of western Ecuador and Peru. Our identification is based on an isolated left petrosal bone, which exhibits a variety of derived diagnostic features of mylodontid sloths in general, e.g., the presence of an epitympanic recess, and the genus Glossotherium in particular, including a reduced anteroventral process of the tegmen tympani. This represents only the second published record of the genus Glossotherium from outside continental South America, and is a substantial range extension for the species G. tropicorum. The present study also represents the first published description of a mylodontid sloth fossil from Trinidad. The specimen is part of a collection that was initially documented in an unpublished Master’s thesis, and that includes additional sloths and other Pleistocene mammals. This fauna confirms the presence of extensive savanna-type habitats on Trinidad during the Pleistocene, and is consistent with the presence of a land bridge connection between the island and mainland South America at that time.
There is no universally accepted definition of “actionable” science at this time. This chapter aims to present a comprehensive perspective on what actionable science entails, delving into its historical context, current understanding, and the prevalent misconceptions across academia, industry, and the public. Our goal is to redefine the concept of “actionability” in scientific research through a rigorous, scientific approach, fostering consensus and unity in evaluating the short-term and long-term value of scientific endeavors. While our exploration centers primarily on the realms of Earth and environmental sciences, we will also touch upon the foundational principles of physics and their influence on environmental sciences, as well as their broader implications for decision-making within human society. This marks our effort to establish a precise definition for “actionable” science and propose a quantitative mathematical framework for gauging the degree of actionability. It will lay down the stepping stones for the following chapters to further explore strategies for enhancing the practical application of scientific research.
The study of Critical Zone (CZ) biogeochemistry in Intensively Managed Landscapes is a study of transitions. Large-scale anthropogenic inputs in the form of agricultural practices have induced significant shifts in the transport and transformation of water, carbon, and nutrients across the landscape. Disentangling the present-day complexity of physical, biological, and hydrologic CZ processes in intensively managed landscapes requires us to first understand the interplay between underlying natural processes which have occurred over geologic time scales from the overpowering, comparatively abrupt onset of intensive agricultural practices that have dominated the landscape in recent centuries. Modeling provides a unique advantage to extricate such complex processes. Advancements in recent years have improved our ability to elucidate (1) the coevolution of soil organic carbon storage, movement, and decomposition under climate and land cover changes, (2) the impacts of intensive agricultural management practices on age-nutrient dynamics and their consequential modification of rates and landscape fluxes, and (3) the integral regulatory role of vegetation and root exudation on CZ biogeochemical processes. In this chapter, we will review several recent models developed in the Intensively Managed Landscape Critical Zone Observatory in Illinois, USA that advance our understanding of critical transitions in biogeochemical dynamics due to intensive management and discuss future challenges.
Climate-induced evolution will determine population persistence in a changing world. However, finding natural systems in which to study these responses has been a barrier to estimating the impact of global change on a broad scale. Here we hypothesize that isolated sky islands (SI) and adjacent mountain chains (MC) can serve as natural laboratories for studying the impact of long-term climatic pressures on natural populations. We used greenhouse common garden trees to test whether populations on SI exposed to hot and dry climates since the Pleistocene have diverged from populations on MC, and if populations on SI have converged in their evolutionary responses. We show: (1) in the southwestern U.S., isolated SI are significantly hotter and drier than adjacent MC, (2) populations of Populus angustifolia from SI have diverged from MC in reproductive and productivity traits, (3) these traits (cloning and aboveground biomass, respectively) are significantly correlated, suggesting a genetic linkage between the traits, and (4) that the observed phenotypic change is driven both by natural selection and genetic drift. These results suggest that long-lived tree populations on distantly related SI have evolved in response to long-term selective pressures and genetic drift by converging on similar phenotypes and diverging from phenotypes on MC. These shifts are towards potentially beneficial phenotypes for population persistence in a changing world. These results also suggest that the SI-MC comparison is an ideal natural laboratory, as well as predictive framework, for studying responses to climate change across the globe.
Theory predicts that threatened species living in small populations will experience high levels of inbreeding that will increase their genetic load, but recent work suggests that the impact of load may be minimized by purging resulting from long‐term population bottlenecks. Empirical studies that examine this idea using genome‐wide estimates of inbreeding and genetic load in threatened species are limited. Here we use individual genome resequencing data to compare levels of inbreeding, levels of genetic load (estimated as mutation load), and population history in threatened Eastern massasauga rattlesnakes (Sistrurus catenatus), which exist in small isolated populations, and closely‐related yet outbred Western massasauga rattlesnakes (S. tergeminus). In terms of inbreeding, S. catenatus genomes had a greater number of ROHs of varying sizes, indicating sustained inbreeding through repeated bottlenecks when compared to S. tergeminus. At the species level, outbred S. tergeminus had higher genome‐wide levels of mutation load in the form of greater numbers of derived deleterious mutations compared to S. catenatus, presumably due to long‐term purging of deleterious mutations in S. catenatus. In contrast, mutations that escaped species‐level drift effects within S. catenatus populations were in general more frequent and more often found in homozygous genotypes than in S. tergeminus, suggesting a reduced efficiency of purifying selection in smaller S. catenatus populations for most mutations. Our results support an emerging idea that the historical demography of a threatened species has a significant impact on the type of genetic load present, which impacts implementation of conservation actions such as genetic rescue.
Quaternary glacial cycles often altered species’ geographic distributions, which in turn altered the geographic structure of species’ genetic diversity. In many cases, glacial expansion forced species in temperate climates to contract their ranges and reside in small pockets of suitable habitat (refugia), where they were likely to interact closely with other species, setting the stage for potential gene exchange. These introgression events, in turn, would have degraded species boundaries, making the inference of phylogenetic relationships challenging. Using high‐throughput sequence data, we employ a combination of species distribution models and hybridization tests to assess the effect of glaciation on the geographic distributions, phylogenetic relationships, and patterns of gene flow of five species of Penstemon subgenus Dasanthera, long‐lived shrubby angiosperms distributed throughout the Pacific Northwest of North America. Surprisingly, we find that rather than reducing their ranges to small refugia, most Penstemon subgenus Dasanthera species experienced increased suitable habitat during the Last Glacial Maximum relative to the present day. We also find substantial evidence for gene exchange between species, with the bulk of introgression events occurring in or near the Klamath Mountains of southwestern Oregon and northwestern California. Subsequently, our phylogenetic inference reveals blurred taxonomic boundaries in the Klamath Mountains, where introgression is most prevalent. Our results question the classical paradigm of temperate species’ responses to glaciation and highlight the importance of contextualizing phylogenetic inference with species’ histories of introgression.
This book is designed as an introduction to the biodiversity, natural history, habitats, and ecosystems of the Chicago Region. The primary goal was to write a concise, informative, field guide–sized book with species descriptions and photos of organisms in all the major taxonomic groups that can be readily observed in the region. There are already many wonderful, specialized field guides to specific groups of species in the region: birds, trees, insects, etc. This book is intended as a good first reference guide that has value in its breadth of coverage of different groups of organisms. The scope of coverage for this field guide is defined as the 7-county Chicago metropolitan area: Cook, Lake, DuPage, Will, McHenry, Kane, and Kendall counties. The book an includes species accounts, descriptions, and color photos of 555 species from the region: 189 herbaceous plants; 53 woody plants, 14 spore plants and lichens, 21 fungi, 13 fishes, 24 amphibians and reptiles, 90 birds, 22 mammals, 112 insects, and 17 non-insect invertebrates.
Species were selected with preference for the following attributes: 1) native to region; 2) common enough to be readily encountered; 3) characteristic of specific important or unique natural habitats in the region.
Each species narrative is written to include interesting and engaging information about the ecology, behavior, ethnobotany, and/or natural history of each species.
This chapter introduces ecoregional green roofs by discussing the development of native plant communities, the history of modern green roofs, and some observations about ecoregional green roofs. It examines the development of the natural vegetation in the western U.S. and Canada and the kinds of plant communities that make up ecoregions appropriate for different forms of green roofs. The history of green roof origins and the development of ecoregional green roofs provide insight into the growth of the modern green roof industry in Europe and North America. Original intentions for green roofs can be misguided, as design decisions or maintenance practices can be out of line with the vegetation selected, or the microclimate of the roof. Several early examples of built ecoregional green roofs highlight successes and lessons learned. Although the conceptual framework laid out in Chap. 1 (and Chap. 2) can be applied anywhere, the climate characteristics for green roofs growing west of the 100th meridian provide background and rationale for the targeted regions of this book. Our knowledge and research literature is only beginning to include the analysis of ecoregional green roofs located in cities where plants experience prolonged exposure to heat and drought, or both.
Previous studies have found mixed results regarding the relationship between beta diversity and latitude. In addition, by influencing local environmental heterogeneity, land use may modify spatial taxonomic and functional variability among communities causing biotic differentiation or homogenization. We tested 1) whether taxonomic and functional beta diversities among streams within watersheds differ between subtropical and boreal regions and 2) whether land use is related to taxonomic and functional beta diversities in both regions. We sampled aquatic insects in 100 subtropical (Brazil) and 100 boreal (Finland) streams across a wide gradient of land use, including agriculture and exotic planted, secondary, and native forests. We calculated beta diversity at the watershed scale (among 5 streams in each watershed). We found higher taxonomic beta diversity among subtropical than among boreal streams, whereas functional beta diversity was similar between the 2 regions. Total land use was positively correlated with taxonomic and functional beta diversity among subtropical streams, while local environmental heterogeneity was positively cor- related with beta diversity among boreal streams. We suggest that different types and intensities of land use may in- crease among-stream heterogeneity, promoting distinct insect assemblage compositions among streams. Our findings also suggest that beta diversity patterns and their underlying determinants are highly context dependent.
Aim
Repeated cycles of Pleistocene glaciation have influenced phylogeographic structure of taxa on New Zealand's South Island. Many taxa became restricted to refugia at either end of the island during glaciation, resulting in an area of low endemicity in central South Island. This area of low endemism is typified by the so‐called beech (or biotic) gap, where the absence of Nothofagus forest (and many other plant and invertebrate taxa) has been attributed to repeated glaciation. Some taxa, however, appear to have persisted in situ in localized refugia within the biotic gap. We test these alternative hypotheses in a large flightless alpine wētā (grasshopper).
Location
Southern Alps, South Island, New Zealand.
Taxon
Hemideina maori Pictet & Saussure, 1891 (Orthoptera: Anostostomatidae).
Methods
We used phylogeographic analysis of mitochondrial cytochrome c oxidase I (cox1) and 25 nuclear DNA (nuDNA) markers to test for Pleistocene glacial microrefugia within the current montane South Island range of Hemideina maori.
Results
We identified eight deeply differentiated mtDNA lineages with limited sharing of haplotypes among populations. Genetic differentiation assessed using nuDNA revealed a similar pattern, with three groups broadly corresponding to the deepest mtDNA splits. The central South Island region exhibits substantial endemic mtDNA diversity and a distinctive nuclear lineage.
Main conclusions
These results indicate that H. maori likely persisted in microrefugia within the biotic gap during glaciation. These deep lineages are estimated to have started diverging prior to the initiation of glaciation, up to 3 Ma. These results add to a growing number of Southern Hemisphere examples of deep phylogeographic differentiation in glaciated alpine regions compared to Europe and North America, probably reflecting less intense glaciation. We suggest that other Southern Alps species showing northern and southern clades alone are more montane than alpine, and were reliant on warmer habitat to the north and south during glacial eras. Thus, there are species‐specific responses to climatic processes, influenced by distinctive habitat requirements and physiological traits.
Climate variability is the most important force affecting distributional range dynamics of common and widespread species with important impacts on biogeographic patterns. This study integrates phylogeography with distributional analyses to understand the demographic history and range dynamics of a widespread bird species, the Ruffed Grouse (Bonasa umbellus), under several climate change scenarios. For this, I used an ecological niche modeling approach, together with Bayesian based phylogeographic analysis and landscape genetics, to develop robust inferences regarding this species’ demographic history and range dynamics. The model’s predictions were mostly congruent with the present distribution of the Ruffed Grouse. However, under the Last Glacial Maximum bioclimatic conditions, the model predicted a substantially narrower distribution than the present. The predictions for the Last Glacial Maximum also showed three allopatric refugia in south-eastern and west-coast North America, and a cryptic refugium in Alaska. The prediction for the Last Interglacial showed two separate distributions to the west and east of the Rocky Mountains. In addition, the predictions for 2050 and 2070 indicated that the Ruffed Grouse will most likely show slight range shifts to the north and will become more widely distributed than in the past or present. At present, effective population connectivity throughout North America was weakly positively correlated with Fst values. That is, the species’ distribution range showed a weak isolation-by-resistance pattern. The extended Bayesian Skyline Plot analysis, which provided good resolution of the effective population size changes over the Ruffed Grouse’s history, was mostly congruent with ecological niche modelling predictions for this species. This study offers the first investigation of the late-Quaternary history of the Ruffed Grouse based on ecological niche modelling and Bayesian based demographic analysis. The species’ present genetic structure is significantly affected by past climate changes, particularly during the last 130 kybp. That is, this study offers valuable evidence of the ‘expansion–contraction’ model of North America’s Pleistocene biogeography.
Quaternary glacial cycles often altered species’ geographic distributions, which in turn altered the geographic structure of a species’ genetic diversity. In many cases, glacial expansion forced species in temperate climates to contract their ranges and reside in small pockets of suitable habitat (refugia), where they were likely to interact closely with other species, setting the stage for potential gene exchange. These introgression events, in turn, would have degraded species boundaries, making the inference of phylogenetic relationships challenging. Using high-throughput sequence data, we employ a combination of species distribution models, models of demographic history, and hybridization tests to assess the effect of glaciation on the geographic distributions, phylogenetic relationships, and patterns of gene flow of five species of Penstemon subgenus Dasanthera , long-lived shrubby angiosperms distributed throughout the Pacific Northwest of North America. Surprisingly, we find that rather than reducing their ranges to small refugia, most Penstemon subgenus Dasanthera species experienced increases in suitable habitat during the Last Glacial Maximum. We also find substantial evidence for gene exchange between species, with the bulk of introgression events occurring in or near the Klamath Mountains of southwestern Oregon and northwestern California. Subsequently, our phylogenetic inference reveals blurred taxonomic boundaries in the Klamath Mountains, where introgression is most prevalent. Our results question the classical paradigm of temperate species’ responses to glaciation, and highlight the importance of contextualizing phylogenetic inference with the demographic histories of the species of interest.
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