Faunal record identifies Bering isthmus conditions as constraint to end-Pleistocene migration to the New World

Beringia and the peopling of the Western Hemisphere

Did Beringian environments represent an ecological barrier to humans until less than 15 000 years ago or was access to the Americas controlled by the spatial-temporal distribution of North American ice sheets? Beringian environments varied with respect to climate and biota, especially in the two major areas of exposed continental shelf. The East Siberian Arctic Shelf ('Great Arctic Plain' (GAP)) supported a dry steppe-tundra biome inhabited by a diverse large-mammal community, while the southern Bering-Chukchi Platform ('Bering Land Bridge' (BLB)) supported mesic tundra and probably a lower large-mammal biomass. A human population with west Eurasian roots occupied the GAP before the Last Glacial Maximum (LGM) and may have accessed mid-latitude North America via an interior ice-free corridor. Re-opening of the corridor less than 14 000 years ago indicates that the primary ancestors of living First Peoples, who already had spread widely in the Americas at this time, probably dispersed from the NW Pacific coast. A genetic 'arctic signal' in non-arctic First Peoples suggests that their parent population inhabited the GAP during the LGM, before their split from the former. We infer a shift from GAP terrestrial to a subarctic maritime economy on the southern BLB coast before dispersal in the Americas from the NW Pacific coast.

Lions and brown bears colonized North America in multiple synchronous waves of dispersal across the Bering Land Bridge

The Bering Land Bridge connecting North America and Eurasia was periodically exposed and inundated by oscillating sea levels during the Pleistocene glacial cycles. This land connection allowed the intermittent dispersal of animals, including humans, between Western Beringia (far northeast Asia) and Eastern Beringia (northwest North America), changing the faunal community composition of both continents. The Pleistocene glacial cycles also had profound impacts on temperature, precipitation and vegetation, impacting faunal community structure and demography. While these palaeoenvironmental impacts have been studied in many large herbivores from Beringia (e.g., bison, mammoths, horses), the Pleistocene population dynamics of the diverse guild of carnivorans present in the region are less well understood, due to their lower abundances. In this study, we analyse mitochondrial genome data from ancient brown bears (Ursus arctos; n = 103) and lions (Panthera spp.; n = 39), two megafaunal carnivorans that dispersed into North America during the Pleistocene. Our results reveal striking synchronicity in the population dynamics of Beringian lions and brown bears, with multiple waves of dispersal across the Bering Land Bridge coinciding with glacial periods of low sea levels, as well as synchronous local extinctions in Eastern Beringia during Marine Isotope Stage 3. The evolutionary histories of these two taxa underline the crucial biogeographical role of the Bering Land Bridge in the distribution, turnover and maintenance of megafaunal populations in North America.

Phylogeny and evolution of the genus Cervus (Cervidae, Mammalia) as revealed by complete mitochondrial genomes

Mitochondrial DNA (mtDNA) lineages are recognized as important components of intra- and interspecific biodiversity, and allow to reveal colonization routes and phylogeographic structure of many taxa. Among these is the genus Cervus that is widely distributed across the Holarctic. We obtained sequences of complete mitochondrial genomes from 13 Cervus taxa and included them in global phylogenetic analyses of 71 Cervinae mitogenomes. The well-resolved phylogenetic trees confirmed Cervus to be monophyletic. Molecular dating based on several fossil calibration points revealed that ca. 2.6 Mya two main mitochondrial lineages of Cervus separated in Central Asia, the Western (including C. hanglu and C. elaphus) and the Eastern (comprising C. albirostris, C. canadensis and C. nippon). We also observed convergent changes in the composition of some mitochondrial genes in C. hanglu of the Western lineage and representatives of the Eastern lineage. Several subspecies of C. nippon and C. hanglu have accumulated a large portion of deleterious substitutions in their mitochondrial protein-coding genes, probably due to drift in the wake of decreasing population size. In contrast to previous studies, we found that the relic haplogroup B of C. elaphus was sister to all other red deer lineages and that the Middle-Eastern haplogroup E shared a common ancestor with the Balkan haplogroup C. Comparison of the mtDNA phylogenetic tree with a published nuclear genome tree may imply ancient introgressions of mtDNA between different Cervus species as well as from the common ancestor of South Asian deer, Rusa timorensis and R. unicolor, to the Cervus clade.

Prehistoric perspectives can help interpret the present: 14,000 years of moose (Alces alces L) in the Western Arctic

Rapidly changing climate at high latitudes has triggered a search for bellwethers of ecological change there. If the initial signs of change can be identified, perhaps we can predict where these changes will lead. Large-bodied, terrestrial, herbivores are potential candidates for bellwether taxa because of the key roles they play in some ecological communities. Here we assemble historical, archaeological and paleontological records of moose (<i>Alces alces</i> Linnaeus, 1758.) from the western Arctic and Subarctic. Results show that rather than having recently invaded tundra regions in response to post-Little Ice Age warming, moose have inhabited river corridors several hundred kilometers north of the closed, boreal forest since they first colonized North America across the Bering Land Bridge ca. 14,000 years ago. The combination of high mobility, fluctuation-prone metapopulations, and reliance on early successional vegetation makes changes in the northern range limits of moose undependable bellwethers for other biotic responses to changing climate. The history of moose at high latitudes illustrates how understanding what happened in prehistory is useful for correctly assigning significance and cause to present-day ecological changes.

Novel alleles gained during the Beringian isolation period

During the Last Glacial Maximum, a small band of Siberians entered the Beringian corridor, where they persisted, isolated from gene flow, for several thousand years before expansion into the Americas. The ecological features of the Beringian environment, coupled with an extended period of isolation at small population size, would have provided evolutionary opportunity for novel genetic variation to arise as both rare standing variants and new mutations were driven to high frequency through both neutral and directed processes. Here we perform a full genome investigation of Native American populations in the Thousand Genomes Project Phase 3 to identify unique high frequency alleles that can be dated to an origin in Beringia. Our analyses demonstrate that descendant populations of Native Americans harbor 20,424 such variants, which is on a scale comparable only to Africa and the Out of Africa bottleneck. This is consistent with simulations of a serial founder effects model. Tests for selection reveal that some of these Beringian variants were likely driven to high frequency by adaptive processes, and bioinformatic analyses suggest possible phenotypic pathways that were under selection during the Beringian Isolation period. Specifically, pathways related to cardiac processes and melanocyte function appear to be enriched for selected Beringian variants.

Phylogeography of Artemisia frigida (Anthemideae, Asteraceae) based on genotyping-by-sequencing and plastid DNA data: Migration through Beringia

Artemisia frigida is a temperate grassland species that has the largest natural range among its genus, with occurrences across the temperate grassland biomes of Eurasia and North America. Despite its wide geographic range, we know little about the species' distribution history. Hence, we conducted a phylogeographical study to test the hypothesis that the species' distribution pattern is related to a potential historical migration over the 'Bering land bridge'. We applied two molecular approaches: genotyping-by-sequencing (GBS) and Sanger sequencing of the plastid intergenic spacer region (rpl32 - trnL) to investigate genetic differentiation and relatedness among 21 populations from North America, Middle Asia, Central Asia and the Russian Far East. Furthermore, we identified the ploidy level of individuals based on GBS data. Our results indicate that A. frigida originated in Asia, spread northwards to the Far East and then to North America across the Bering Strait. We found a pronounced genetic structuring between Middle and Central Asian populations with mixed ploidy levels, tetraploids in the Far East, and nearly exclusively diploids in North America except for one individual. According to phylogenetic analysis, two populations of Kazakhstan (KZ2 and KZ3) represent the most likely ancestral diploids that constitute the basally branching lineages, and subsequent polyploidization has occurred on several occasions independently. Mantel tests revealed weak correlations between genetic distance and geographical distance and climatic conditions, which indicates that paleoclimatic fluctuations may have more profoundly influenced A. frigida's spatial genetic structure and distribution than the current environment.

Genome-wide SNP analysis of three moose subspecies at the southern range limit in the contiguous United States

Genome-wide evaluations of genetic diversity and population structure are important for informing management and conservation of trailing-edge populations. North American moose (Alces alces) are declining along portions of the southern edge of their range due to disease, species interactions, and marginal habitat, all of which may be exacerbated by climate change. We employed a genotyping by sequencing (GBS) approach in an effort to collect baseline information on the genetic variation of moose inhabiting the species’ southern range periphery in the contiguous United States. We identified 1920 single nucleotide polymorphisms (SNPs) from 155 moose representing three subspecies from five states: A. a. americana (New Hampshire), A. a. andersoni (Minnesota), and A. a. shirasi (Idaho, Montana, and Wyoming). Molecular analyses supported three geographically isolated clusters, congruent with currently recognized subspecies. Additionally, while moderately low genetic diversity was observed, there was little evidence of inbreeding. Results also indicated > 20% shared ancestry proportions between A. a. shirasi samples from northern Montana and A. a. andersoni samples from Minnesota, indicating a putative hybrid zone warranting further investigation. GBS has proven to be a simple and effective method for genome-wide SNP discovery in moose and provides robust data for informing herd management and conservation priorities. With increasing disease, predation, and climate related pressure on range edge moose populations in the United States, the use of SNP data to identify gene flow between subspecies may prove a powerful tool for moose management and recovery, particularly if hybrid moose are more able to adapt.

Phylogenetics and phylogeography of red deer mtDNA lineages during the last 50 000 years in Eurasia

The present phylogeographic pattern of red deer in Eurasia is not only a result of the contraction of their distribution range into glacial refugia and postglacial expansion, but probably also an effect of replacement of some red deer s.l. mtDNA lineages by others during the last 50 000 years. To better recognize this process, we analysed 501 sequences of mtDNA cytochrome b, including 194 ancient and 75 contemporary samples newly obtained for this study. The inclusion of 161 radiocarbon-dated samples enabled us to study the phylogeny in a temporal context and conduct divergence-time estimation and molecular dating. Depending on methodology, our estimate of divergence between Cervus elaphus and Cervus canadensis varied considerably (370 000 or 1.37 million years BP, respectively). The divergence times of genetic lineages and haplogroups corresponded to large environmental changes associated with stadials and interstadials of the Late Pleistocene. Due to the climatic oscillations, the distribution of C. elaphus and C. canadensis fluctuated in north–south and east–west directions. Some haplotypes dated to pre-Last Glacial Maximum periods were not detected afterwards, representing possibly extinct populations. We indicated with a high probability the presence of red deer sensu lato in south-eastern Europe and western Asia during the Last Glacial Maximum.

Peopling of the Americas as inferred from ancient genomics

In less than a decade, analyses of ancient genomes have transformed our understanding of the Indigenous peopling and population history of the Americas. These studies have shown that this history, which began in the late Pleistocene epoch and continued episodically into the Holocene epoch, was far more complex than previously thought. It is now evident that the initial dispersal involved the movement from northeast Asia of distinct and previously unknown populations, including some for whom there are no currently known descendants. The first peoples, once south of the continental ice sheets, spread widely, expanded rapidly and branched into multiple populations. Their descendants-over the next fifteen millennia-experienced varying degrees of isolation, admixture, continuity and replacement, and their genomes help to illuminate the relationships among major subgroups of Native American populations. Notably, all ancient individuals in the Americas, save for later-arriving Arctic peoples, are more closely related to contemporary Indigenous American individuals than to any other population elsewhere, which challenges the claim-which is based on anatomical evidence-that there was an early, non-Native American population in the Americas. Here we review the patterns revealed by ancient genomics that help to shed light on the past peoples who created the archaeological landscape, and together lead to deeper insights into the population and cultural history of the Americas.

Ancient horse genomes reveal the timing and extent of dispersals across the Bering Land Bridge

The Bering Land Bridge (BLB) last connected Eurasia and North America during the Late Pleistocene. Although the BLB would have enabled transfers of terrestrial biota in both directions, it also acted as an ecological filter whose permeability varied considerably over time. Here we explore the possible impacts of this ecological corridor on genetic diversity within, and connectivity among, populations of a once wide-ranging group, the caballine horses (Equus spp.). Using a panel of 187 mitochondrial and eight nuclear genomes recovered from present-day and extinct caballine horses sampled across the Holarctic, we found that Eurasian horse populations initially diverged from those in North America, their ancestral continent, around 1.0-0.8 million years ago. Subsequent to this split our mitochondrial DNA analysis identified two bidirectional long-range dispersals across the BLB ~875-625 and ~200-50 thousand years ago, during the Middle and Late Pleistocene. Whole genome analysis indicated low levels of gene flow between North American and Eurasian horse populations, which probably occurred as a result of these inferred dispersals. Nonetheless, mitochondrial and nuclear diversity of caballine horse populations retained strong phylogeographical structuring. Our results suggest that barriers to gene flow, currently unidentified but possibly related to habitat distribution across Beringia or ongoing evolutionary divergence, played an important role in shaping the early genetic history of caballine horses, including the ancestors of living horses within Equus ferus.

Ancient Beringian paleodiets revealed through multiproxy stable isotope analyses

The earliest Native Americans have often been portrayed as either megafaunal specialists or generalist foragers, but this debate cannot be resolved by studying the faunal record alone. Stable isotope analysis directly reveals the foods consumed by individuals. We present multi-tissue isotope analyses of two Ancient Beringian infants from the Upward Sun River site (USR), Alaska (~11,500 years ago). Models of fetal bone turnover combined with seasonally-sensitive taxa show that the carbon and nitrogen isotope composition of USR infant bone collagen reflects maternal diets over the summer. Using comparative faunal isotope data, we demonstrate that although terrestrial sources dominated maternal diets, salmon was also important, supported by carbon isotope analysis of essential amino acids and bone bioapatite. Tooth enamel samples indicate increased salmon use between spring and summer. Our results do not support either strictly megafaunal specialists or generalized foragers but indicate that Ancient Beringian diets were complex and seasonally structured.

The Potyviruses: An Evolutionary Synthesis Is Emerging

In this review, encouraged by the dictum of Theodosius Dobzhansky that "Nothing in biology makes sense except in the light of evolution", we outline the likely evolutionary pathways that have resulted in the observed similarities and differences of the extant molecules, biology, distribution, etc. of the potyvirids and, especially, its largest genus, the potyviruses. The potyvirids are a family of plant-infecting RNA-genome viruses. They had a single polyphyletic origin, and all share at least three of their genes (i.e., the helicase region of their CI protein, the RdRp region of their NIb protein and their coat protein) with other viruses which are otherwise unrelated. Potyvirids fall into 11 genera of which the potyviruses, the largest, include more than 150 distinct viruses found worldwide. The first potyvirus probably originated 15,000-30,000 years ago, in a Eurasian grass host, by acquiring crucial changes to its coat protein and HC-Pro protein, which enabled it to be transmitted by migrating host-seeking aphids. All potyviruses are aphid-borne and, in nature, infect discreet sets of monocotyledonous or eudicotyledonous angiosperms. All potyvirus genomes are under negative selection; the HC-Pro, CP, Nia, and NIb genes are most strongly selected, and the PIPO gene least, but there are overriding virus specific differences; for example, all turnip mosaic virus genes are more strongly conserved than those of potato virus Y. Estimates of dN/dS (ω) indicate whether potyvirus populations have been evolving as one or more subpopulations and could be used to help define species boundaries. Recombinants are common in many potyvirus populations (20%-64% in five examined), but recombination seems to be an uncommon speciation mechanism as, of 149 distinct potyviruses, only two were clear recombinants. Human activities, especially trade and farming, have fostered and spread both potyviruses and their aphid vectors throughout the world, especially over the past five centuries. The world distribution of potyviruses, especially those found on islands, indicates that potyviruses may be more frequently or effectively transmitted by seed than experimental tests suggest. Only two meta-genomic potyviruses have been recorded from animal samples, and both are probably contaminants.

The Invasion Hierarchy: Ecological and Evolutionary Consequences of Invasions in the Fossil Record

Species invasions are pervasive in Earth history, yet the ecological and evolutionary consequences vary greatly. Ancient invasion events can be organized in a hierarchy of increasing invasion intensity from ephemeral invasions to globally pervasive invasive regimes. Each level exhibits emergent properties exceeding the sum of interactions at lower levels. Hierarchy levels correspond to, but do not always exactly correlate with, geographic extent of invasion success. The ecological impacts of lower-level impacts can be negligible or result in temporary community accommodation. Invasion events at moderate to high levels of the hierarchy permanently alter ecological communities, regional faunas, and global ecosystems. The prevalence of invasive species results in evolutionary changes by fostering niche evolution, differential survival of ecologically generalized taxa, faunal homogenization, and suppressing speciation. These impacts can contribute to mass extinctions and biodiversity crises that alter the trajectory of ecological and evolutionary patterns of life. The fossil record provides a long-term record of how invasion impacts may scale up through time, which can augment ecological studies of modern species invasions.

Bayesian Statistics in Archaeology

Null hypothesis significance testing (NHST) is the most common statistical framework used by scientists, including archaeologists. Owing to increasing dissatisfaction, however, Bayesian inference has become an alternative to these methods. In this article, we review the application of Bayesian statistics to archaeology. We begin with a simple example to demonstrate the differences in applying NHST and Bayesian inference to an archaeological problem. Next, we formally define NHST and Bayesian inference, provide a brief historical overview of their development, and discuss the advantages and limitations of each method. A review of Bayesian inference and archaeology follows, highlighting the applications of Bayesian methods to chronological, bioarchaeological, zooarchaeological, ceramic, lithic, and spatial analyses. We close by considering the future applications of Bayesian statistics to archaeological research.

A new terrestrial palaeoenvironmental record from the Bering Land Bridge and context for human dispersal

Palaeoenvironmental records from the now-submerged Bering Land Bridge (BLB) covering the Last Glacial Maximum (LGM) to the present are needed to document changing environments and connections with the dispersal of humans into North America. Moreover, terrestrially based records of environmental changes are needed in close proximity to the re-establishment of circulation between Pacific and Atlantic Oceans following the end of the last glaciation to test palaeo-climate models for the high latitudes. We present the first terrestrial temperature and hydrologic reconstructions from the LGM to the present from the BLB's south-central margin. We find that the timing of the earliest unequivocal human dispersals into Alaska, based on archaeological evidence, corresponds with a shift to warmer/wetter conditions on the BLB between 14 700 and 13 500 years ago associated with the early Bølling/Allerød interstadial (BA). These environmental changes could have provided the impetus for eastward human dispersal at that time, from Western or central Beringia after a protracted human population standstill. Our data indicate substantial climate-induced environmental changes on the BLB since the LGM, which would potentially have had significant influences on megafaunal and human biogeography in the region.

Genetic signature of natural selection in first Americans

When humans moved from Asia toward the Americas over 18,000 y ago and eventually peopled the New World they encountered a new environment with extreme climate conditions and distinct dietary resources. These environmental and dietary pressures may have led to instances of genetic adaptation with the potential to influence the phenotypic variation in extant Native American populations. An example of such an event is the evolution of the fatty acid desaturases (FADS) genes, which have been claimed to harbor signals of positive selection in Inuit populations due to adaptation to the cold Greenland Arctic climate and to a protein-rich diet. Because there was evidence of intercontinental variation in this genetic region, with indications of positive selection for its variants, we decided to compare the Inuit findings with other Native American data. Here, we use several lines of evidence to show that the signal of FADS-positive selection is not restricted to the Arctic but instead is broadly observed throughout the Americas. The shared signature of selection among populations living in such a diverse range of environments is likely due to a single and strong instance of local adaptation that took place in the common ancestral population before their entrance into the New World. These first Americans peopled the whole continent and spread this adaptive variant across a diverse set of environments.

The colonization history of British water vole (Arvicola amphibius (Linnaeus, 1758)): origins and development of the Celtic fringe

The terminal Pleistocene and Early Holocene, a period from 15 000 to 18 000 Before Present (BP), was critical in establishing the current Holarctic fauna, with temperate-climate species largely replacing cold-adapted ones at mid-latitudes. However, the timing and nature of this process remain unclear for many taxa, a point that impacts on current and future management strategies. Here, we use an ancient DNA dataset to test more directly postglacial histories of the water vole (Arvicola amphibius, formerly A terrestris), a species that is both a conservation priority and a pest in different parts of its range. We specifically examine colonization of Britain, where a complex genetic structure can be observed today. Although we focus on population history at the limits of the species' range, the inclusion of additional European samples allows insights into European postglacial colonization events and provides a molecular perspective on water vole taxonomy.

Postglacial viability and colonization in North America's ice-free corridor

During the Last Glacial Maximum, continental ice sheets isolated Beringia (northeast Siberia and northwest North America) from unglaciated North America. By around 15 to 14 thousand calibrated radiocarbon years before present (cal. kyr bp), glacial retreat opened an approximately 1,500-km-long corridor between the ice sheets. It remains unclear when plants and animals colonized this corridor and it became biologically viable for human migration. We obtained radiocarbon dates, pollen, macrofossils and metagenomic DNA from lake sediment cores in a bottleneck portion of the corridor. We find evidence of steppe vegetation, bison and mammoth by approximately 12.6 cal. kyr bp, followed by open forest, with evidence of moose and elk at about 11.5 cal. kyr bp, and boreal forest approximately 10 cal. kyr bp. Our findings reveal that the first Americans, whether Clovis or earlier groups in unglaciated North America before 12.6 cal. kyr bp, are unlikely to have travelled by this route into the Americas. However, later groups may have used this north-south passageway.

Occasional recombination of a selfish X-chromosome may permit its persistence at high frequencies in the wild

The sex-ratio X-chromosome (SR) is a selfish chromosome that promotes its own transmission to the next generation by destroying Y-bearing sperm in the testes of carrier males. In some natural populations of the fly Drosophila neotestacea, up to 30% of the X-chromosomes are SR chromosomes. To investigate the molecular evolutionary history and consequences of SR, we sequenced SR and standard (ST) males at 11 X-linked loci that span the ST X-chromosome and at seven arbitrarily chosen autosomal loci from a sample of D. neotestacea males from throughout the species range. We found that the evolutionary relationship between ST and SR varies among individual markers, but genetic differentiation between SR and ST is chromosome-wide and likely due to large chromosomal inversions that suppress recombination. However, SR does not consist of a single multilocus haplotype: we find evidence for gene flow between ST and SR at every locus assayed. Furthermore, we do not find long-distance linkage disequilibrium within SR chromosomes, suggesting that recombination occurs in females homozygous for SR. Finally, polymorphism on SR is reduced compared to that on ST, and loci displaying signatures of selection on ST do not show similar patterns on SR. Thus, even if selection is less effective on SR, our results suggest that gene flow with ST and recombination between SR chromosomes may prevent the accumulation of deleterious mutations and allow its long-term persistence at relatively high frequencies.

Pleistocene Overkill and North American Mammalian Extinctions

Clovis groups in Late Pleistocene North America occasionally hunted several now extinct large mammals. But whether their hunting drove 37 genera of animals to extinction has been disputed, largely for want of kill sites. Overkill proponents argue that there is more archaeological evidence than we ought to expect, that humans had the wherewithal to decimate what may have been millions of animals, and that the appearance of humans and the disappearance of the fauna is too striking to be a mere coincidence. Yet, there is less to these claims than meets the eye. Moreover, extinctions took place amid sweeping climatic and environmental changes as the Pleistocene came to an end. It has long been difficult to link those changes to mammalian extinctions, but the advent of ancient DNA, coupled with high-resolution paleoecological, radiocarbon, and archeological records, should help disentangle the relative role of changing climates and people in mammalian extinctions.

Mitochondrial genome diversity at the Bering Strait area highlights prehistoric human migrations from Siberia to northern North America

The patterns of prehistoric migrations across the Bering Land Bridge are far from being completely understood: there still exists a significant gap in our knowledge of the population history of former Beringia. Here, through comprehensive survey of mitochondrial DNA genomes retained in 'relic' populations, the Maritime Chukchi, Siberian Eskimos, and Commander Aleuts, we explore genetic contribution of prehistoric Siberians/Asians to northwestern Native Americans. Overall, 201 complete mitochondrial sequences (52 new and 149 published) were selected in the reconstruction of trees encompassing mtDNA lineages that are restricted to Coastal Chukotka and Alaska, the Canadian Arctic, Greenland, and the Aleutian chain. Phylogeography of the resulting mtDNA genomes (mitogenomes) considerably extends the range and intrinsic diversity of haplogroups (eg, A2a, A2b, D2a, and D4b1a2a1) that emerged and diversified in postglacial central Beringia, defining independent origins of Neo-Eskimos versus Paleo-Eskimos, Aleuts, and Tlingit (Na-Dene). Specifically, Neo-Eskimos, ancestral to modern Inuit, not only appear to be of the High Arctic origin but also to harbor Altai/Sayan-related ancestry. The occurrence of the haplogroup D2a1b haplotypes in Chukotka (Sireniki) introduces the possibility that the traces of Paleo-Eskimos have not been fully erased by spread of the Neo-Eskimos or their descendants. Our findings are consistent with the recurrent gene flow model of multiple streams of expansions to northern North America from northeastern Eurasia in late Pleistocene-early Holocene.

Using Ancient DNA to Understand Evolutionary and Ecological Processes

Ancient DNA provides a unique means to record genetic change through time and directly observe evolutionary and ecological processes. Although mostly based on mitochondrial DNA, the increasing availability of genomic sequences is leading to unprecedented levels of resolution. Temporal studies of population genetics have revealed dynamic patterns of change in many large vertebrates, featuring localized extinctions, migrations, and population bottlenecks. The pronounced climate cycles of the Late Pleistocene have played a key role, reducing the taxonomic and genetic diversity of many taxa and shaping modern populations. Importantly, the complex series of events revealed by ancient DNA data is seldom reflected in current biogeographic patterns. DNA preserved in ancient sediments and coprolites has been used to characterize a range of paleoenvironments and reconstruct functional relationships in paleoecological systems. In the near future, genome-level surveys of ancient populations will play an increasingly important role in revealing, calibrating, and testing evolutionary processes.

Assessing prehistoric genetic structure and diversity of North American elk (Cervus elaphus) populations in Alberta, Canada

North American elk (Cervus elaphus L., 1758) are an important component of Canada’s natural ecosystems. Overhunting and habitat decline in the 19th century led to the near eradication of Rocky Mountain elk (Cervus elaphus nelsoni Bailey, 1935) and Manitoban elk (Cervus elaphus manitobensis Millais, 1915) within Alberta. Though elk populations have been restored within provincial and national parks, it is unknown to what degree historic population declines affected overall genetic diversity and population structuring of the two subspecies. This study targeted 551 bp of mitochondrial D-loop DNA from 50 elk remains recovered from 16 archaeological sites (2260 BCE (before common era) to 1920 CE (common era)) to examine the former genetic diversity and population structure of Alberta’s historic elk populations. Comparisons of ancient and modern haplotype and nucleotide diversity suggest that historic population declines reduced the mitochondrial diversity of Manitoban elk, while translocation of animals from Yellowstone National Park in the early 20th century served to maintain the diversity of Rocky Mountain populations. Gene flow between the two subspecies was significantly higher in the past than today, suggesting that the two subspecies previously formed a continuous population. These data on precontact genetic diversity and gene flow in Alberta elk provide essential baseline data integral for elk management and conservation in the province.