Postglacial Migration Research Articles

Forests and foragers: exploitation of wood resources by Mesolithic and para-Neolithic societies in north-eastern Poland

Newly acquired palaeobotanical data, including pollen, charred and uncharred wood, provided an exhaustive overview of the temporal changes in woodlands, which changes are due to the cumulative effect of natural processes and the long-term impact of pre-agrarian societies. We used the unique advantage of the peat bog archaeological site at Szczepanki located on an island in the former Lake Staświn (Masurian Lake District) to get an overview of wood exploitation throughout the Stone Age. Special attention was paid to the period of the most intense settlement, the period of the para-Neolithic Zedmar culture. This culture is interesting due to its economy having not been fully recognized so far, especially with respect to the use of plant resources. The evidence from Szczepanki confirmed the use of 16 arboreal taxa, accessible in local woodlands, as a source of timber by foragers. The majority of both unworked wood and fragments bearing traces of processing has been discovered in layers corresponding to the Zedmar period. An important role in the economy was played by wood with medium or low mechanical properties that was however fissile and amenable to woodworking. In addition, other useful properties such as flexibility, lightness, water resistance, strength and ease of splitting were favoured in the selection. The temporal distribution of wood remains in cultural layers at Szczepanki was convergent with a pollen record documenting the course of postglacial migration and local growth of particular taxa, as well as with the archaeologically documented changes in the intensity and time frame of the settlement.

Ice-age persistence and genetic isolation of the disjunct distribution of larch in Alaska.

Larix laricina (eastern larch, tamarack) is a transcontinental North American conifer with a prominent disjunction in the Yukon isolating the Alaskan distribution from the rest of its range. We investigate whether in situ persistence during the last glacial maximum (LGM) or long‐distance postglacial migration from south of the ice sheets resulted in the modern‐day Alaskan distribution. We analyzed variation in three chloroplast DNA regions of 840 trees from a total of 69 populations (24 new sampling sites situated on both sides of the Yukon range disjunction pooled with 45 populations from a published source) and conducted ensemble species distribution modeling (SDM) throughout Canada and United States to hindcast the potential range of L. laricina during the LGM. We uncovered the genetic signature of a long‐term isolation of larch populations in Alaska, identifying three endemic chlorotypes and low levels of genetic diversity. Range‐wide analysis across North America revealed the presence of a distinct Alaskan lineage. Postglacial gene flow across the Yukon divide was unidirectional, from Alaska toward previously glaciated Canadian regions, and with no evidence of immigration into Alaska. Hindcast SDM indicates one of the broadest areas of past climate suitability for L. laricina existed in central Alaska, suggesting possible in situ persistence of larch in Alaska during the LGM. Our results provide the first unambiguous evidence for the long‐term isolation of L. laricina in Alaska that extends beyond the last glacial period and into the present interglacial period. The lack of gene flow into Alaska along with the overall probability of larch occurrence in Alaska being currently lower than during the LGM suggests that modern‐day Alaskan larch populations are isolated climate relicts of broader glacial distributions, and so are particularly vulnerable to current warming trends.

Inference of biogeographic history by formally integrating distinct lines of evidence: genetic, environmental niche and fossil

A primary focus of historical biogeography is to understand changes in species ranges, abundance and genetic connectivity, and changes in community composition. Traditionally, biogeographic inference has relied on distinct lines of evidence, including DNA sequences, fossils and hindcasted ecological niche models. In this review we propose that the development of integrative modeling approaches that leverage multiple distinct data types from diverse disciplines has the potential to revolutionize the field of biogeography. Although each data type contains information on a distinct aspect of species’ biogeographic histories, few studies formally integrate multiple types in analysis. For example, post hoc congruence among analyses based on different data types (e.g. fossils and genetics) is commonly assumed to indicate likely biogeographic histories. Unfortunately, analyses of different data often reach discordant conclusions. Thus, fundamental and unresolved debates continue regarding speed and timing of postglacial migration, location and size of glacial refugia, and degree of long distance dispersal. Formal statistical integration can help address these issues. More specifically, formal integration can leverage all available evidence, account for inherent biases associated with different data types, and quantify data and process uncertainty. Novel, quantitative integration of data and models across fields is now possible due to recent advances in cyberinfrastructure, spatial modeling, online and aggregated ecological databases, data processing and quantitative methods. Our purpose is to make the case for and give examples of rigorous integration of genetic, fossil and environmental/occurrence data for inferring biogeographic history. In particular, we 1) review the need for such a framework; 2) explain common data types and approaches used to infer biogeographic history (and the challenges with each); 3) review state‐of‐the‐art examples of data integration in biogeography; 4) lay out a series of novel, suggested improvements on current methods; and 5) provide an outlook on technical feasibility and future opportunities.

Western and eastern post-glacial migration pathways shape the genetic structure of sycamore maple (Acer pseudoplatanus L.) in Germany

Sycamore maple (Acer pseudoplatanus L.) is a broadleaved forest tree species mainly occurring in mountainous areas of Europe, preferring fresh to moist, deep, calcareous soils. As was the case with other important forest tree species, sycamore maple was absent from the area north of the Alps during the last ice age. Therefore, we investigated the origin of sycamore maple in this area and its genetic variation across the landscape as the result of its postglacial migration into this area. We compared our results with the current delineation of sycamore maple into regions of provenance in Germany. Altogether 1043 trees from Germany, but also, in few cases, from bordering countries, were analysed using 11 nuclear and one chloroplast microsatellite (SSR) markers. Both the analysis of chloroplast (cpDNA) haplotypes and the Bayesian cluster analysis based on nuclear SSR data revealed distinct genetic structures of sycamore maple in Germany, suggesting more than one origin. The spatial distribution of a particular cpDNA haplotype (haplotype ‘105’) might be the result of a migration event with an eastern origin, probably along the Eastern Alps, which could have occurred during the Holocene. The other haplotype (haplotype ‘102’) might be of (south-) western origin, representing a migration pathway along the Western Alps. This hypothesis is further supported by a Bayesian cluster analysis based on nuclear SSRs. We identified two clusters, one distributed in the western part of the study area and one in the eastern. Between them, a zone of genetic introgression occurs, where populations exhibit a mixed membership to both clusters. This zone of genetic admixture is narrower in the south. An analysis of the landscape shape confirms that average genetic differentiation per distance unit is higher in the south. This is also in agreement with higher genetic distances between regions of provenance in the south. The mountainous landscape of this region could have contributed to this higher genetic differentiation, by posing geographic barriers to gene flow. On the contrary, wide-scale seed movement, also beyond the limit of native range, as well as a flat relief could have resulted in a wider zone of admixture in the north. Based on our results, we argue that the current delineation of provenance regions for sycamore maple in Germany fits to the inferred patterns of genetic differentiation.

Summer Climatic Moisture Balances for Yukon Xerophytic Grassland Slopes and Their Late-Wisconsinan Counterparts: Are Present-Day Grasslands Beringian Relicts?

Summer climatic moisture balances (precipitation vs. potential evapotranspiration) for topographic slopes favored by present-day xerophytic boreal grasslands (SSW aspects with 61% – 65% gradients) in southwest Yukon were compared to their unglaciated late-Wisconsinan (14 000 – 12 000 cal yr BP) Beringian counterparts. The purpose was to determine whether present-day grasslands are ecologically plausible Beringian relicts or analogues. The Beringian climate was represented by meteorological stations with average July temperatures 4˚C colder than those of present-day grassland areas; all were from Arctic locations. The most commonly occupied grassland slopes received maximum local solar radiation and likely represented the warmest topographic positions in the landscape. Their summer evapotranspiration demands exceeded the 200 mm moisture supply by 189 mm. The same slopes had late-Wisconsinan summer moisture balances of −57 to −101 mm because of colder and shorter growing seasons. Moisture balances for late-Wisconsinan SSW slopes were similar to those of present-day WNW – NW aspects, which do not support grasslands. Differences in moisture deficits indicated present-day xerophytic grasslands were improbable Beringian in situ relicts or analogues. Alternatively, it was hypothesized that present-day Calamagrostis purpurascens communities developed during the Holocene Thermal Maximum (11 000 – 9000 cal yr BP), whereas Hesperostipa comata communities formed less than 3000 years ago after postglacial migration of the species from central North America.

Northwest passage to Scandinavia.

Genomes from hunter-gatherers dated to around 9,000 years ago reveal two early postglacial migrations into Scandinavia: an initial migration from the south and a second coastal migration north of the Scandinavian ice sheet.

Influence of northern limit range on genetic diversity and structure in a widespread North American tree, sugar maple (Acer saccharum Marshall).

Due to climate change, the ranges of many North American tree species are expected to shift northward. Sugar maple (Acer saccharum Marshall) reaches its northern continuous distributional limit in northeastern North America at the transition between boreal mixed‐wood and temperate deciduous forests. We hypothesized that marginal fragmented northern populations from the boreal mixed wood would have a distinct pattern of genetic structure and diversity. We analyzed variation at 18 microsatellite loci from 23 populations distributed along three latitudinal transects (west, central, and east) that encompass the continuous–discontinuous species range. Each transect was divided into two zones, continuous (temperate deciduous) and discontinuous (boreal mixed wood), based on sugar maple stand abundance. Respective positive and negative relationships were found between the distance of each population to the northern limit (D_north), and allelic richness (A R) and population differentiation (F ST). These relations were tested for each transect separately; the pattern (discontinuous–continuous) remained significant only for the western transect. structure analysis revealed the presence of four clusters. The most northern populations of each transect were assigned to a distinct group. Asymmetrical gene flow occurred from the southern into the four northernmost populations. Southern populations in Québec may have originated from two different postglacial migration routes. No evidence was found to validate the hypothesis that northern populations were remnants of a larger population that had migrated further north of the species range after the retreat of the ice sheet. The northernmost sugar maple populations possibly originated from long‐distance dispersal.

Population genomics of Mesolithic Scandinavia: Investigating early postglacial migration routes and high-latitude adaptation

Scandinavia was one of the last geographic areas in Europe to become habitable for humans after the Last Glacial Maximum (LGM). However, the routes and genetic composition of these postglacial migrants remain unclear. We sequenced the genomes, up to 57× coverage, of seven hunter-gatherers excavated across Scandinavia and dated from 9,500–6,000 years before present (BP). Surprisingly, among the Scandinavian Mesolithic individuals, the genetic data display an east–west genetic gradient that opposes the pattern seen in other parts of Mesolithic Europe. Our results suggest two different early postglacial migrations into Scandinavia: initially from the south, and later, from the northeast. The latter followed the ice-free Norwegian north Atlantic coast, along which novel and advanced pressure-blade stone-tool techniques may have spread. These two groups met and mixed in Scandinavia, creating a genetically diverse population, which shows patterns of genetic adaptation to high latitude environments. These potential adaptations include high frequencies of low pigmentation variants and a gene region associated with physical performance, which shows strong continuity into modern-day northern Europeans.

STUDIES ON THE GLACIAL REFUGIA OF FOREST TREES ON BALKAN PENINSULA

During the Ice Age the southern parts of Europe, including Balkans, remained practically unaffected by glaciations and served as refugia for many plant and animal species. However, even within the framework of each glacial refugia, the conditions were not homogeneous and isolated “hot spots” appeared that had led to “refugia within refugia”. The territory of Balkan Peninsula could be subdivided into different zones, which are of different importance from the point of view of formation of the present day biodiversity. Tree species are particularly suitable for studies of inter-glacial and post-glacial migrations, due to their important ecological role in shaping the environmental conditions. Today, studying of these issues is greatly facilitated by introducing of genetic markers, allowing precise tracing of post-glacial migrations. The topic is less studied in the Balkan Peninsula, even though the region is considered one of the most important European refugia. A brief review of the more important studies in this respect is presented and the prospects and importance of such studies is discussed.

Early postglacial recolonisation, refugial dynamics and the origin of a major biodiversity hotspot. A case study from the Malá Fatra mountains, Western Carpathians, Slovakia

While general trends in Central European postglacial recolonisation dynamics are relatively well known, we often lack studies on intermediate (meta-population, landscape) scales. Such studies are needed to increase our understanding of, for example, the location of refugia; emergence of endemism, rates and trajectories of postglacial migrations; and anthropogenic landscape changes. Here, we focused on the outer Western Carpathian mountain chain Malá Fatra, which is currently characterised by high biodiversity and endemism and is thus considered a likely refugium of the Last Glacial period for the temperate biota of Eastern–Central Europe. We used molluscs and vascular plants as reference taxonomic groups and supported palaeoenvironmental interpretations of their (sub)fossil assemblages using high-resolution geochemical data. Generally, postglacial biotic successions from the study region fit the standard developmental pattern well in Middle and Eastern European uplands. Nevertheless, we found important biogeographically based peculiarities. In total, more than 50 species per (sub)fossil community at the reference site Valča, including 30 woodland species and 11 Carpathian endemites, make site of the highest known Holocene mollusc species diversity in Europe. Our palaeoecological analysis of this long-term biodiversity hotspot suggests that the Western Carpathians were likely an important source of the postglacial recolonisation of Central Europe by forest biota and, at the same time, an area of refugium-based endemism.

Local environment rather than past climate determines community composition of mountain stream macroinvertebrates across Europe.

Community assembly is determined by a combination of historical events and contemporary processes that are difficult to disentangle, but eco-evolutionary mechanisms may be uncovered by the joint analysis of species and genetic diversity across multiple sites. Mountain streams across Europe harbour highly diverse macroinvertebrate communities whose composition and turnover (replacement of taxa) among sites and regions remain poorly known. We studied whole-community biodiversity within and among six mountain regions along a latitudinal transect from Morocco to Scandinavia at three levels of taxonomic hierarchy: genus, species and haplotypes. Using DNA barcoding of four insect families (>3100 individuals, 118 species) across 62 streams, we found that measures of local and regional diversity and intraregional turnover generally declined slightly towards northern latitudes. However, at all hierarchical levels we found complete (haplotype) or high (species, genus) turnover among regions (and even among sites within regions), which counters the expectations of Pleistocene postglacial northward expansion from southern refugia. Species distributions were mostly correlated with environmental conditions, suggesting a strong role of lineage- or species-specific traits in determining local and latitudinal community composition, lineage diversification and phylogenetic community structure (e.g., loss of Coleoptera, but not Ephemeroptera, at northern sites). High intraspecific genetic structure within regions, even in northernmost sites, reflects species-specific dispersal and demographic histories and indicates postglacial migration from geographically scattered refugia, rather than from only southern areas. Overall, patterns were not strongly concordant across hierarchical levels, but consistent with the overriding influence of environmental factors determining community composition at the species and genus levels.

Genetic variation patterns of American chestnut populations at EST-SSRs

The objective of this study is to analyze patterns of genetic variation at genic expressed sequence tag – simple sequence repeats (EST-SSRs) and at chloroplast DNA markers in populations of American chestnut (Castanea dentata Borkh.) to assist in conservation and breeding efforts. Allelic diversity at EST-SSRs decreased significantly from southwest to northeast along the Appalachian range, suggesting repeated founder events during postglacial migration. Comparatively high allelic diversity in Ontario, northwest of the Appalachian range, suggested more recent long-distance dispersal. Clinal variation of allele frequencies along the Appalachian axis was also in accordance with postglacial colonization from one refugium southwest of the Appalachian range. We observed clustering of the northwestern population from Ontario with southwestern populations and sharing of a rare chloroplast haplotype among western populations across the whole latitudinal range. This pattern is consistent with a divergence of postglacial migration routes and higher levels of more recent potentially human-mediated gene exchange between populations west of the Appalachian range. Population pairs east and west of the Appalachian axis showed pronounced allele frequency differences over a small geographic range. These patterns of genetic variation should be considered when sampling reproductive material for conservation and breeding.

No obvious genetic erosion, but evident relict status at the westernmost range edge of the Pontic-Pannonian steppe plant Linum flavum L. (Linaceae) in Central Europe.

We investigate patterns of genetic variation along an east–west transect of Central European populations of Linum flavum and interpret the Quaternary history of its peripheral populations, especially those at the westernmost isolated range edge, discussing their migrations and possible relict status. We defined our peripheral transect across three study regions from Central Hungary, eastern Austria to southwestern Germany. Using AFLP fingerprinting and cpDNA sequence variation (rpL16 intron, atpI‐H), we analyzed 267 and 95 individuals, respectively, representing each study region by four populations. Hierarchical AMOVA (AFLPs) indicated significant variation among study regions (12% of total variance) and moderate differentiation between populations (10%). Population differentiation was high at the westernmost range edge (11.5%, Germany), but also in the east (13.4%, Hungary), compared to the Austrian study region (8.6%). Correspondingly, AFLP diversity was highest in the center of the study transect in eastern Austria. CpDNA haplotypes support a pattern of regional structuring with the strongest separation of the westernmost range edge, and some haplotype sharing among Austrian and Hungarian individuals. Equilibrating nucleotide versus haplotype diversity patterns, the highly diverse populations at the Pannonian range edge (Austria) indicate long‐term persistence, while Central Pannonian populations are obviously effected by recent bottlenecks. Intermediate nucleotide, but high haplotype diversity within the westernmost exclave (Swabian Alb), is indicative of a founder bottleneck during its pre‐LGM or early postglacial migration history, followed by sufficient time to accumulate cpDNA variation. The not obviously reduced genetic diversity and distinctiveness of L. flavum at the westernmost range edge suggest a long‐term persistence (relict status) of populations in this region, where the species has survived probably even the Würm glaciation in extra‐Mediterranean refugia. This genetic relict variation represents an important part of the overall genetic diversity found in the western periphery of this steppe plant and highlights the high conservation priority of respective gene pools.

Geographic genetic structure of Iberian columbines (gen. Aquilegia)

Southern European columbines (genus Aquilegia) are involved in active processes of diversification, and the Iberian Peninsula offers a privileged observatory to witness the process. Studies on Iberian columbines have provided significant advances on species diversification, but we still lack a complete perspective of the genetic diversification in the Iberian scenario. This work explores how genetic diversity of the genus Aquilegia is geographically structured across the Iberian Peninsula. We used Bayesian clustering methods, principal coordinates analyses, and NJ phenograms to assess the genetic relationships among 285 individuals from 62 locations and detect the main lineages. Genetic diversity of Iberian columbines consists of five geographically structured lineages, corresponding to different Iberian taxa. Differentiation among lineages shows particularly complex admixture patterns at Northeast and highly homogeneous toward Northwest and Southeast. This geographic genetic structure suggests the existence of incomplete lineage sorting and interspecific hybridization as could be expected in recent processes of diversification under the influence of quaternary postglacial migrations. This scenario is consistent with what is proposed by the most recent studies on European and Iberian columbines, which point to geographic isolation and divergent selection by habitat specialization as the main diversification drivers of the Iberian Aquilegia complex.

Tabula rasa in the Patagonian Channels? The phylogeography of Oreobolus obtusangulus (Cyperaceae).

The extent of the Pleistocene glaciations in the Patagonian Channel region (southwesternmost South America) and their impact on the vegetation there are largely unknown. Whether the regional flora was wiped out completely (tabula rasa) or survived in ice-free pockets (insitu survival) is still an open question. The molecular imprint of either scenario should still be visible in extant populations. Therefore, DNA sequence data of Oreobolus obtusangulus Gaudich. (Cyperaceae) were analysed. This species is an abundant constituent of Patagonian cushion peat bogs, one of the Patagonian Channel region's major vegetation types. Three hundred and eighty-four individuals from 48 populations were sequenced for two chloroplast (ycf3-psaA and trnQUUG -psbK intergenic spacers) and 14 nuclear loci containing simple sequence repeats (SSRs; microsatellites). Phylogenetic reconstructions and the geographic distribution of genetic diversity revealed that the species was split into three main lineages whose general distributions comprise three separate major regions, that is, south-central Chile, Fuego-Patagonia and the East Patagonian Andes, which probably constitute glacial refugia. Postglacial migration fronts formed a suture zone with high levels of genetic diversity in the Northwest Patagonian Andes, where remnants of a supposedly ancestral lineage were also found to be locally restricted to a single population (Huinay). The heavily glaciated Patagonian Channels were likely recolonized from the northwest, and partly from the south. Although the westernmost Patagonian Channel population (Estero Bachem) harboured private SSR alleles (singletons) and showed slightly elevated genetic diversity, it remained unclear whether this population actually survived insitu. This study helps fill a major gap in reconstructing the Pleistocene vegetation history of West and Andean Patagonia.

The paleosymbiosis hypothesis: host plants can be colonised by root symbionts that have been inactive for centuries to millenia.

Paleoecologists have speculated that post-glacial migration of tree species could have been facilitated by mycorrhizal symbionts surviving glaciation as resistant propagules belowground. The general premise of this idea, which we call the 'paleosymbiosis hypothesis', is that host plants can access and be colonised by fungal root symbionts that have been inactive for millennia. Here, we explore the plausibility of this hypothesis by synthesising relevant findings from a diverse literature. For example, the paleoecology literature provided evidence of modern roots penetrating paleosols containing ancient (>6000 years) fungal propagules, though these were of unknown condition. With respect to propagule longevity, the available evidence is of mixed quality, but includes convincing examples consistent with the paleosymbiosis hypothesis (i.e. >1000 years viable propagules). We describe symbiont traits and environmental conditions that should favour the development and preservation of an ancient propagule bank, and discuss the implications for our understanding of soil symbiont diversity and ecosystem functioning. We conclude that the paleosymbiosis hypothesis is plausible in locations where propagule deposition and preservation conditions are favourable (e.g. permafrost regions). We encourage future belowground research to consider and explore the potential temporal origins of root symbioses.

Molecular markers provide evidence for a broad-fronted recolonisation of the widespread calcareous grassland species Sanguisorba minor from southern and cryptic northern refugia.

Calcareous grasslands belong to the most species-rich and endangered habitats in Europe. However, little is known about the origin of the species typically occurring in these grasslands. In this study we analysed the glacial and post-glacial history of Sanguisorba minor, a typical plant species frequently occurring in calcareous grasslands. The study comprised 38 populations throughout the whole distribution range of the species across Europe. We used molecular markers (AFLP) and applied Bayesian cluster analysis as well as spatial principal components analysis (sPCA) to identify glacial refugia and post-glacial migration routes to Central Europe. Our study revealed significant differences in the level of genetic variation and the occurrence of rare fragments within populations of S.minor and a distinct separation of eastern and western lineages. The analyses uncovered traditional southern but also cryptic northern refugia and point towards a broad fronted post-glacial recolonisation. Based on these results we postulate that incomplete lineage sorting may have contributed to the detected pattern of genetic variation and that S.minor recolonised Central Europe post-glacially from Iberia and northern glacial refugia in France, Belgium or Germany. Our results highlight the importance of refugial areas for the conservation of intraspecific variation in calcareous grassland species.

Species distribution modeling and molecular markers suggest longitudinal range shifts and cryptic northern refugia of the typical calcareous grassland species Hippocrepis comosa (horseshoe vetch).

Calcareous grasslands belong to the most diverse, endangered habitats in Europe, but there is still insufficient information about the origin of the plant species related to these grasslands. In order to illuminate this question, we chose for our study the representative grassland species Hippocrepis comosa (Horseshoe vetch). Based on species distribution modeling and molecular markers, we identified the glacial refugia and the postglacial migration routes of the species to Central Europe. We clearly demonstrate that H. comosa followed a latitudinal and due to its oceanity also a longitudinal gradient during the last glacial maximum (LGM), restricting the species to southern refugia situated on the Peninsulas of Iberia, the Balkans, and Italy during the last glaciation. However, we also found evidence for cryptic northern refugia in the UK, the Alps, and Central Germany. Both species distribution modeling and molecular markers underline that refugia of temperate, oceanic species such as H. comosa must not be exclusively located in southern but also in western of parts of Europe. The analysis showed a distinct separation of the southern refugia into a western cluster embracing Iberia and an eastern group including the Balkans and Italy, which determined the postglacial recolonization of Central Europe. At the end of the LGM, H. comosa seems to have expanded from the Iberian refugium, to Central and Northern Europe, including the UK, Belgium, and Germany.

The genetic characterization of an isolated remnant population of an endangered rodent (Cricetus cricetus L.) using comparative data: implications for conservation

Estimates of genetic diversity and phylogenetic affiliation represent an important resource for biodiversity assessment and a valuable guide to conservation and management. We have found a new population (Jawor—JW) of the common hamster Cricetus cricetus in western Poland that is remote from the nearest populations by 235–300 km. With the objective of genetically characterizing of this population, we compared it with other populations from Poland and Germany by taking into account sequences of four mitochondrial DNA genes and variation at 10 microsatellite loci. The JW population exhibited low levels of genetic diversity and allelic and haplotype richness, which likely reflects its extreme isolation. This factor, coupled with inbreeding and genetic drift, are major threats to JW. A neighbor-joining tree based on mtDNA haplotypes shows that JW clusters among samples representing the Central subgroup that is known from central Germany but that has not yet been identified in Poland. Findings presented here improve our understanding of the spread and diversification of the common hamster. We offer the following hypotheses to explain the observed pattern of mtDNA haplotype distribution: JW could be a byproduct of postglacial migrations or back-migrations from eastern refugia to the western part of Europe, or/and be a result of population and habitat fragmentation. We recommend translocation of individuals as an effective management strategy, both at the level of Central phylogeographic group and at the species level, to overcome the negative consequences of inbreeding and geographical isolation of the JW population.

Mapping Post-Glacial expansions: The Peopling of Southwest Asia

Archaeological, palaeontological and geological evidence shows that post-glacial warming released human populations from their various climate-bound refugia. Yet specific connections between these refugia and the timing and routes of post-glacial migrations that ultimately established modern patterns of genetic variation remain elusive. Here, we use Y-chromosome markers combined with autosomal data to reconstruct population expansions from regional refugia in Southwest Asia. Populations from three regions in particular possess distinctive autosomal genetic signatures indicative of likely refugia: one, in the north, centered around the eastern coast of the Black Sea, the second, with a more Levantine focus, and the third in the southern Arabian Peninsula. Modern populations from these three regions carry the widest diversity and may indeed represent the most likely descendants of the populations responsible for the Neolithic cultures of Southwest Asia. We reveal the distinct and datable expansion routes of populations from these three refugia throughout Southwest Asia and into Europe and North Africa and discuss the possible correlations of these migrations to various cultural and climatic events evident in the archaeological record of the past 15,000 years.