Postglacial Recolonization Research Articles

Beech forests as world heritage in aspect to the next extension of the ancient and primeval beech forests of the Carpathians and other regions of Europe world heritage site

Beech forests were first protected under the World Heritage Convention in 2007 as the Primeval Beech Forests of the Carpathians (Slovakia and Ukraine). After two latter extensions in 2011 and 2017, the Natural World Heritage site is currently named the Ancient and Primeval Beech Forests of the Carpathians and Other Regions of Europe (Albania, Austria, Belgium, Bulgaria, Croatia, Germany, Italy, Romania, Slovakia, Slovenia, Spain and Ukraine) and consists of 78 component parts in 12 European countries. It aims to ensure the preservation of beech gene pool, ecosystem and species diversity of beech forests, their future renewal and expansion, in regard to the development and use pressures they encounter and the biodiversity they support. Additionally, this World Heritage site aims to depict the beech expansion after the last Ice Age, spreading over a large percent of the continent to form one of the most significant forest ecosystems in Europe. The third extension nomination has been developed in 2020 and proposes the inscription of additional 30 component parts, a considerable step towards the complete overall picture of post-glacial beech re-colonization process and beech ecosystem diversity across Europe. With this extension 8 additional European countries would join this property, including the Republic of Serbia. The extended property would consist of over 100 component parts in 20 European countries, a pan-European network of protected areas with joint protection and management goals to represent a platform for policy making and knowledge exchange. This paper presents the genesis of this extremely complex World Heritage property and the work done to expand it over the protected beech forests in Serbia, in preparation of the first Natural World Heritage nomination for the Republic of Serbia.

Mitochondrial phylogeography of the Mediterranean horseshoe bat on the Balkan Peninsula

The Balkan Peninsula is identified as one of the major glacial refugia in Europe during the Pleistocene, and it has served as a genetic source for post-glacial recolonization for many temperate species. The aim of this study was to investigate the genetic diversity and phylogeographic patterns of the Mediterranean horseshoe bat, Rhinolophus euryale Blasius 1853, on the Balkan Peninsula. We also analyzed its demographic history and tested the hypothesis that this region was a glacial refugium for this species. We collected 82 samples from 20 localities in the Balkans and Italy and sequenced the mitochondrial D-loop region. Our results revealed low nucleotide but high haplotype diversity, with 20 out of 24 haplotypes reported for the first time. All Balkan and Italian samples belonged to a single genetic clade in the phylogenetic reconstruction, where they clustered together with previously published samples from Turkey, southern France and North Africa. The haplotype network had a star-like pattern that is indicative of recent population expansion. Both mismatch distribution and shallow genetic differentiation also supported the scenario of a sudden demographic expansion. We estimated that expansion within this lineage commenced in the Late Pleistocene. We suggest that the Balkan Peninsula was a glacial refugium for R. euryale.

Genetic structure of the endangered, relict shrub Amygdalus mongolica (Rosaceae) in arid northwest China

In the present study we selected the endangered species Amygdalus mongolica to investigate the influence of climatic fluctuations on the spatial genetic patterns and evolutionary history of organisms in arid northwest China. The intraspecific genetic variation and demographic history of A. mongolica were investigated using two cpDNA sequences (psbK-psbI and trnL-trnF) from 174 individuals in 15 populations across most of its covered range. Significant genetic differentiation among populations was identified, which resulted from fragmented populations coupled with the enhanced aridification and desertification of the Pleistocene. Twelve haplotypes clustered into two clades, corresponding to the Western region (northernmost Gansu, Hexi Corridor and Alxa Left Banner) and the Eastern region (Urad Houqi, Yinshan Mountains, Urad Zhongqi and Daqing Mountains) respectively. Five independent Pleistocene refugia in different mountainous areas were identified. Amygdalus mongolica has likely experienced westward shifts from refugia along the margins of the Ulanbuhe and Tengger deserts, and also postglacial re-colonisation northward along the Hexi Corridor.

Phylogeography and genetic connectivity of the marine macro-alga Sargassum ilicifolium (Phaeophyceae, Ochrophyta) in the northwestern Pacific1.

The evolutionary influences of historical and contemporary factors on the population connectivity and phylogeographic structure of a brown seaweed, Sargassum ilicifolium, were elucidated using the nuclear ITS2 and mitochondrial COI markers for the collections newly sampled within its distribution range in the northwestern Pacific (NWP). Significant genetic structure at variable levels was identified between populations (pairwise FST ) and among populations grouped by geographical proximity (ΦCT among regions). The adjacent groups of populations with moderate structure revealed from AMOVA appeared to have high genetic connectivity. However, a lack of genealogical concordance with the geographic distribution was uncovered for S.ilicifolium from the NWP. Such genetic homogeneity is interpreted as a result of the interaction between postglacial recolonization and dynamic oceanic current regimes in the region. Two separated glacial refugia, the South China Sea and the Okinawa Trough, in the marginal seas of east China were recognized based on the presence of endemic haplotypes and high haplotype diversity in the populations at southern China and northeast of Taiwan. Populations persisting in these refugia may have served as the source for recolonization in the NWP with the rise of sea level during the warmer interglacial periods. The role of oceanic currents in maintaining genetic connectivity of S.ilicifolium in the region was further corroborated by the coherence between the direction of oceanic currents and that of gene flow, especially along the eastern coast of Taiwan. This study underlines the interaction between historical postglacial recolonization and contemporary coastal hydrodynamics in contributing to population connectivity and distribution for this tropical seaweed in the NWP.

Contrasting elevational patterns of genetic variation in Euptelea pleiospermum along mountains at the core and edges of its latitudinal range

Patterns of genetic variation along both latitudinal and elevational gradients have been intensively studied in the last few decades. To date, however, elevational patterns of genetic diversity and gene flow remain rarely compared for the same species along mountains at the center and edges of its latitudinal range. We used nuclear microsatellite analysis to compare the elevational patterns of both genetic variation and gene flow for Euptelea pleiospermum along elevational transects on the Qinling (33°N; leading edge), Shennongjia (31°N; mid-latitude), and Emei (29°N; rear edge) Mountains in China. First, we found no elevational pattern of genetic diversity along the two marginal mountains, but we found higher genetic diversity in the middle-altitude populations than in the low- and high-altitudes along the mid-latitude mountain. Second, there was no obvious genetic structure along the two marginal mountains, but individuals along the mid-latitude mountain were clustered into the upper and lower groups. Third, the contemporary gene flow along the two marginal mountains was higher than that along the mid-latitude mountain. Lastly, we found no isolation-by-distance along all three mountains and a significant isolation-by-elevation along the mid-latitude mountain but not along the two marginal mountains. Our results demonstrated that the elevational patterns of both genetic variation and gene flow for a tree species are different along mountains at the core and edges of its latitudinal range. These differences are likely associated with the discrepancies in spatial isolation, ecological stability, and vegetation types, but not historical events (e.g., post-glacial recolonization) at different latitudes.

Evidences for a shared history for spectacled salamanders, haplotypes and climate

The so-called glacial refugia, formed during the Pleistocene climatic oscillations, played a major role in shaping the distribution of European species, triggering migrations or isolating populations. Many of these events were recently investigated by genetic data, mainly for the European Last Glacial stage, in the Iberic, Italian and Greek-Balkan peninsulas. The amphibian genus Salamandrina, the most ancient living salamandrid lineage, was widespread in Europe until the climatic oscillations of Miocene probably forced it to shelter in the only suitable territory at that time, the Apennines. Nowadays this genus is endemic of peninsular Italy with two parapatric species, S. perspicillata and S. terdigitata, sharing an area of secondary contact formed after the Last Glacial Maximum. Climate is generally identified as the key factor for the interpretation of genetic data. In this research, we directly measure climate influences on the two Salamandrina known species through Ensemble Modelling techniques and post-modelling GIS analyses, integrating updated genetic data in this process. Our results confirm the hypotheses of southwards (and subsequent northwards) shifts, identify glacial refugia and corridors used for the post-glacial re-colonization. Finally, we map a contact zone deserving more sampling effort to disentangle the introgression and hybridization observed.

Postglacial range expansion shaped the spatial genetic structure in a marine habitat‐forming species: Implications for conservation plans in the Eastern Adriatic Sea

AbstractAimUnderstanding how historical and contemporary processes shaped and maintain spatial patterns of genetic diversity is a major goal for conservation biologists. Here, we characterized the pattern of neutral genetic diversity and we inferred underlying processes in the habitat‐forming octocoral Paramuricea clavata in the Adriatic Sea, a peculiar phylogeographic region of the Mediterranean Sea.LocationEastern coast of the Adriatic Sea.MethodsWe genotyped seven microsatellites in 454 individuals of P. clavata from 13 populations recolonized after the Last Glacial Maximum (LGM). We estimated the levels of contemporary connectivity and genetic drift and we reconstructed the demographic history of these populations.ResultsThe pattern of spatial genetic structure resulted from the combination of hierarchical genetic clusters and isolation by distance (IBD). A significant decrease in genetic diversity and an increase of the frequencies of individual alleles likely due to allele surfing from the south to the north of the area were observed as expected after a postglacial sequential recolonization. Based on maximum likelihood analyses, the foundation of these populations was not linked to dramatic change in population size.Main conclusionOceanographic barriers to gene flow combined to the restricted dispersal of P. clavata likely maintain the hierarchical structure and the IBD pattern. We suggest that the latitudinal genetic gradient results from a northward “serial founder events” recolonization. By integrating patterns and processes, we bridge the gap between the evolutionary and the conservation biology of P. clavata, providing management guidelines, which will benefit the associated coralligenous biodiversity.

Site conditions and recipient plant communities as indicators of the origin of a cryptogenic species. Leucojum vernum L. in North France as a case study

Regional lists of protected species commonly include rare plant species that are found in small, isolated populations at the range margin or disjunct. However, such populations often have suspicious origins and may have been historically introduced and now falsely viewed as native. Here I use a simple community ecology approach to assess whether plant community composition and site features can indicate whether local populations of a rare cryptogenic species are more likely of natural or introduced origin. I took the vernal geophyte Leucojum vernum L. in North France as a case study. Using multivariate analyses I show that L. vernum occurs in various plant communities, which correspond to different sets of environmental conditions. More specifically, several community types clearly reflect an introduced origin, with a discrepancy between L. vernum’s autecology and site features as well as a number of co-occurring anthropophilous species, including xenophytes. These populations are often associated with more or less ancient human artefacts, such as archaeological sites. In contrast, an equal number of community types likely correspond to natural populations, that are all located at the range margin and connected to the core range via a (former) west-flowing river corridor, pleading for a post-glacial recolonization. I conclude that a cryptogenic species, such as L. vernum in this case study, has a “socio-ecological signature” which can indicate whether a given population is more likely native or introduced, and thus informs conservationists on where to prioritize conservation efforts.

Genetic Structure of Lobaria pulmonaria in the Alps as a Result of Post-Glacial Recolonization History

Lerch M., Nadyeina O. & Scheidegger C. 2018: Genetic structure of Lobaria pulmonaria in the Alps as a result of post-glacial recolonization history. – Herzogia 31: 650 – 665.The present-day genetic structure of a species is highly influenced by its history. Quaternary range expansions and contractions had a major impact on the genetic diversity and structure of species, which has implications for presentday conservation strategies of rare and threatened species. The aim of this study was to investigate the genetic structure of Lobaria pulmonaria and its green-algal photobiont Symbiochloris reticulata from the Alps. Here we present the genetic structure of 75 Lobaria pulmonaria populations and we investigated which of three fungal and two algal genetic lineages that were recognized in a broader study on the European phylogeography of this species are present in the Alps and from where postglacial recolonization might have occurred. Our study showed that only the fungal genepool A and the algal genepool R contributed to the recolonization of the Alps. The fungal genepools B1 and B2 were restricted to the eastern and western borders of the Alps but play an important role in the current populations in the Jura Mountains, the Vosges and the Black Forest. The algal genepool S was only found at the southwestern borders of the Alps and we hypothesize that this genepool is adapted to Mediterranean climates. For both symbionts we found a significant positive correlation between longitude and allelic richness, indicating a recolonization of the Alps from a peripheral refugium for genepool A at the eastern border of the Alps or from the Carpathian Mountains.

Effects of glaciation and whole genome duplication on the distribution of the Campanula rotundifolia polyploid complex.

Both intrinsic and extrinsic factors contribute to a species distribution. Among plants, the extrinsic effects of glaciation and intrinsic effects of whole genome duplication are powerful drivers of biogeographical patterns, but the interplay of these factors is poorly understood. Here, we investigate the roles glaciation and whole-genome duplication have played in the evolution of the widespread polyploid complex Campanula rotundifolia. We assessed the cytotype of 37 populations that spanned the geographic and cytotypic range of the C. rotundifolia complex. We constructed a chloroplast phylogeny for these populations and used RAD-seq to create nuclear phylogenies and networks for a subset of 23 populations; and estimated divergence times of major clades using Bayesian estimation of substitution rates. Campanula rotundifolia originated in south-central Europe and underwent range expansion throughout much of Europe and North America. Multiple genome duplications have occurred in C. rotundifolia-at least two tetraploid and three hexaploid formations. Nuclear and chloroplast phylogenies are largely congruent with a history of populations surviving glacial maxima in known Pleistocene refugia in Europe and North America. Divergent European clades are consistent with two disjunct glacial refugia within Europe. North America was colonized by hexaploids derived from Western European lineages. A glacial refugium in Midwestern North America likely facilitated post-glacial recolonization of North America and limited genetic divergence. These results implicate both glaciation and whole-genome duplication as contributing factors to the extant biogeography of C. rotundifolia.

Host specificity driving genetic structure and diversity in ectoparasite populations: Coevolutionary patterns in Apodemus mice and their lice.

A degree of host specificity, manifested by the processes of host–parasite cospeciations and host switches, is assumed to be a major determinant of parasites’ evolution. To understand these patterns and formulate appropriate ecological hypotheses, we need better insight into the coevolutionary processes at the intraspecific level, including the maintenance of genetic diversity and population structure of parasites and their hosts. Here, we address these questions by analyzing large‐scale molecular data on the louse Polyplax serrata and its hosts, mice of the genus Apodemus, across a broad range of European localities. Using mitochondrial DNA sequences and microsatellite data, we demonstrate the general genetic correspondence of the Apodemus/Polyplax system to the scenario of the postglacial recolonization of Europe, but we also show several striking discrepancies. Among the most interesting are the evolution of different degrees of host specificity in closely related louse lineages in sympatry, or decoupled population structures of the host and parasites in central Europe. We also find strong support for the prediction that parasites with narrower host specificity possess a lower level of genetic diversity and a deeper pattern of interpopulation structure as a result of limited dispersal and smaller effective population size.

Phylogeographic pattern of the plane leaf miner, Phyllonorycter platani (STAUDINGER, 1870) (Lepidoptera: Gracillariidae) in Europe

BackgroundThe plane leaf miner, Phyllonorycter platani is a widely distributed insect species on plane trees and has a well-documented colonisation history in Europe over the last century. However, phylogeographic data of the species are lacking.ResultsWe analysed 284 individuals from 38 populations across Europe, Asia, and North America. A 1242 bp fragment of the mitochondrial COI gene and an 893 bp fragment of the 28S rDNA has been Sanger sequenced. Twenty-four haplotypes were detected on the COI gene, and two alleles were identified on the 28S rDNA. We revealed two distinct clades for both markers reflecting the geographic origins, Asia and Europe. The genetic distance between the two main clades is 2.08% on the COI gene and 0.10% on the nuclear DNA.An overlapping zone of the two clades was found across Eastern Europe and the Anatolian Peninsula. We detected heterozygote individuals of the 28S rDNA gene in Moldavia, Ukraine and in the southern part of Turkey. These suggest that the two clades can hybridise. Furthermore, the presence of European type homozygote individuals has been confirmed in the southern part of Turkey as well.ConclusionsWe have shown that both post-glacial recolonization and recent expansion events influenced the present genetic structure of P. platani. The genetic patterns revealed at least two refugia during the last ice age: one in the Balkan Peninsula and the other in the Caucasus region. Recent expansion was detected in some European and Central Asian populations. The two main clades (Europe/Asia) show definite genetic differences; however, several hybrid individuals were found in the overlapping zone as well (stretching over Eastern Europe and the Anatolian Peninsula). Discrepancies in mitochondrial and nuclear data indicate introgressions in the southern part of the Anatolian Peninsula.

Genetic analysis of European red foxes reveals multiple distinct peripheral populations and central continental admixture

Temperate terrestrial species in Europe were hypothesized to have been restricted to southern peninsular refugia (Iberia, Italy, Balkans) during the height of the last glacial period. However, recent analyses of fossil evidence indicate that some temperate species existed outside these areas during the last glacial maximum (LGM). Red foxes (Vulpes vulpes) in particular, could have been distributed across the southern half of the continent, potentially forming one continuous population. To investigate these hypotheses, we used 21 nuclear microsatellite loci and two fragments (768 bp) of mitochondrial DNA to characterize the population structure among a continent-wide sample of 288 European red foxes. We tested whether European red foxes clustered into discrete populations corresponding to the hypothetical peninsular refugia. Additionally, we sought to determine if distinct northern populations were formed after post-glacial recolonization. Our results indicated that only the foxes of Iberia appeared to have remained distinct over a considerable period of time (32–104 kya). Spanish red foxes formed their own genotypic cluster; all mtDNA haplotypes were endemic and closely related, and together both the mitochondrial and nuclear datasets indicated this population contributed little to postglacial recolonization of Northern Europe. In contrast, red foxes from Italy and the Balkans contributed significantly to, or were part of, a wider, admixed population stretching across mid-latitude Europe. In Northern Europe, we identified a Scandinavian population that had an ancestral relationship with red foxes to the south, and a more recent relationship with those to the east, in Russia. We also resolved two distinct populations on the islands of Ireland and Britain that had been separated from one another, and from those on the continent, since the late Pleistocene/mid Holocene (∼4–24 kya).

Genetic diversity maintained among fragmented populations of a tree undergoing range contraction

Dwarf birch (Betula nana) has a widespread boreal distribution but has declined significantly in Britain where populations are now highly fragmented. We analyzed the genetic diversity of these fragmented populations using markers that differ in mutation rate: conventional microsatellites markers (PCR-SSRs), RADseq generated transition and transversion SNPs (RAD-SNPs), and microsatellite markers mined from RADseq reads (RAD-SSRs). We estimated the current population sizes by census and indirectly, from the linkage-disequilibrium found in the genetic surveys. The two types of estimate were highly correlated. Overall, we found genetic diversity to be only slightly lower in Britain than across a comparable area in Scandinavia where populations are large and continuous. While the ensemble of British fragments maintain diversity levels close to Scandinavian populations, individually they have drifted apart and lost diversity; particularly the smaller populations. An ABC analysis, based on coalescent models, favors demographic scenarios in which Britain maintained high levels of genetic diversity through post-glacial re-colonization. This diversity has subsequently been partitioned into population fragments that have recently lost diversity at a rate corresponding to the current population-size estimates. We conclude that the British population fragments retain sufficient genetic resources to be the basis of conservation and re-planting programmes. Use of markers with different mutation rates gives us greater confidence and insight than one marker set could have alone, and we suggest that RAD-SSRs are particularly useful as high mutation-rate marker set with a well-specified ascertainment bias, which are widely available yet often neglected in existing RAD datasets.

Intraspecific mitogenomics of three marine species-at-risk: Atlantic, spotted, and northern wolffish (Anarhichasspp.)

High-resolution mitogenomics of within-species relationships can answer such phylogeographic questions as how species survived the most recent glaciation, as well as identify contemporary factors such as physical barriers, isolation, and gene flow. We examined the mitogenomic population structure of three at-risk species of wolffish: Atlantic (Anarhichas lupus), spotted (A. minor), and northern (A. denticulatus). These species are extensively sympatric across the North Atlantic but exhibit very different life history strategies, a combination that results in concordant and discordant patterns of genetic variation and structure. Wolffish haplogroups were not structured geographically: Atlantic and spotted wolffish each comprised three shallow clades, whereas northern wolffish comprised two deeper but unstructured lineages. We suggest that wolffish species survived in isolation in multiple glacial refugia, either refugia within refugia (Atlantic and spotted wolffish) or more distant refugia (northern wolffish), followed by secondary admixture upon post-glacial recolonisation of the North Atlantic.

Pleistocene Refugia for Calluna vulgaris (L.) Hull Populations in the European Atlantic Region

The distribution of nine chloroplast DNA haplotypes in four insular North-Atlantic and four European coastal Atlantic populations of Calluna vulgaris in the glacial zone of the range has been analyzed in comparison with that in six marginal southern populations in the nonglacial zone of the Atlantic and Mediterranean regions. As a result, two hypothetical Pleistocene refugia (HPRs) for this C. vulgaris population group have been revealed, one in the Cevennes mountain range and the other in the Southern Alps (Trento). Judging from the 1–FST value, it has been found that the group of populations in the glacial Atlantic zone and adjacent European coastal Atlantic region is genetically similar to the HPR in the Cevennes at a highly significant level (p ≥ 0.999) and less similar to the HPR in Trento; however, it differs significantly from other Mediterranean and Atlantic populations. It has been concluded that the most probable hypothetical Pleistocene refugium for the recent C. vulgaris populations of the northeastern Atlantic and European coastal Atlantic regions was in the west of the Mediterranean, in the Cevennes, while the additional refugium was in the Southern Alps. Possible directions of the postglacial dispersal and recolonization of habitats by C. vulgaris populations from the western Mediterranean to the northeast of the Atlantic and to Scandinavia have been revealed.

Post-glacial recolonization of insular Newfoundland across the Strait of Belle Isle gave rise to an endemic subspecies of woodland caribou, Rangifer tarandus terranovae (Bangs, 1896): evidence from mtDNA haplotypes.

Post-glacial origins of woodland caribou (Rangifer tarandus subsp.) on the island of Newfoundland and their relationship to mainland populations have been uncertain. Sequence analysis of 2223 bp of the mitochondrial DNA control region and cytochrome b gene from 233 Newfoundland caribou identified 32 haplotypes in four major clades. Comparison with other Nearctic caribou confirms a closer affinity of the basal Clade A with animals from the mainland, and as an outgroup to Clades B, C, and D that are endemic to the island. This indicates re-entry of caribou to post-glacial Newfoundland across the Strait of Belle Isle from Labrador, rather than from southern coastal refugia. Newfoundland caribou are a distinct subspecies, Rangifer tarandus terranovae (Bangs, 1896). Hierarchical AMOVA shows significant clinal differentiation of the major clades from northwest to southeast across the island. The isolated Avalon Peninsula population in the extreme southeast is genetically depauperate. Founder effects are evident in herds introduced to previously unoccupied areas by wildlife managers over the past 40-50 years. Reindeer introduced in the early 20th century have not contributed to mtDNA diversity in Newfoundland caribou.

Genetic structure and demographic inference of the regular sea urchin Sterechinus neumayeri (Meissner, 1900) in the Southern Ocean: The role of the last glaciation.

One of the most relevant characteristics of the extant Southern Ocean fauna is its resiliency to survive glacial processes of the Quaternary. These climatic events produced catastrophic habitat reductions and forced some marine benthic species to move, adapt or go extinct. The marine benthic species inhabiting the Antarctic upper continental shelf faced the Quaternary glaciations with different strategies that drastically modified population sizes and thus affected the amount and distribution of intraspecific genetic variation. Here we present new genetic information for the most conspicuous regular sea urchin of the Antarctic continental shelf, Sterechinus neumayeri. We studied the patterns of genetic diversity and structure in this broadcast-spawner across three Antarctic regions: Antarctic Peninsula, the Weddell Sea and Adélie Land in East Antarctica. Genetic analyses based on mitochondrial and nuclear markers suggested that S. neumayeri is a single genetic unit around the Antarctic continent. The species is characterized by low levels of genetic diversity and exhibits a typical star-like haplotype genealogy that supports the hypothesis of a single in situ refugium. Based on two mutation rates standardized for this genus, the Bayesian Skyline plot analyses detected a rapid demographic expansion after the Last Glacial Maximum. We propose a scenario of rapid postglacial expansion and recolonization of Antarctic shallow areas from a less ice-impacted refugium where the species survived the LGM. Considering the patterns of genetic diversity and structure recorded in the species, this refugium was probably located in East Antarctica.

Phylogeography and Ecological Niche Modeling Reveal Reduced Genetic Diversity and Colonization Patterns of Skunk Cabbage (Symplocarpus foetidus; Araceae) From Glacial Refugia in Eastern North America.

Alternating glacial and interglacial periods during the Quaternary have dramatically affected the distribution and population genetic structure of plant and animal species throughout the northern hemisphere. Surprisingly, little is known about the post-glacial recolonization history of wetland herbaceous perennials that are widely distributed in the understory of deciduous or mixed deciduous-evergreen forests in eastern North America. In this study, we investigated infraspecific variation among 32 populations of skunk cabbage, Symplocarpus foetidus, to test the hypothesis that the extant species diversity of skunk cabbage is the result of a post-glacial range expansion from southern refugia during the Quaternary Ice Age. A total of 4041 base pairs (bp) of the chloroplast intergenic spacer region (cpDNA) was sequenced from 485 individuals sampled from glaciated (18 populations, 275 individuals) and unglaciated (14 populations, 210 individuals) regions east and west of the Appalachian Mountains. Haplotype number, haplotype diversity, and nucleotide diversity were calculated, and genetic variation within and among populations was assessed by analysis of molecular variance (AMOVA). The geographic pattern of genetic differentiation was further investigated with a spatial analysis of molecular variance (SAMOVA). A total of eight haplotypes and three genetic groups (SAMOVA) were recovered and a much higher haplotype number (eight haplotypes) and haplotype diversity (0.7425) was observed in unglaciated compared to glaciated populations (five haplotypes, haplotype diversity = 0.6099). All haplotypes found in glaciated regions represented a subset of haplotypes found in unglaciated regions. Haplotypes of S. foetidus likely diverged during the Tertiary (mid-Miocene and late Pliocene), predating the last glacial maximum (LGM). Predictions based on ecological niche modeling (ENM) suggested that there was considerably less suitable habitat for skunk cabbage during the LGM, and the habitat range was further south compared to the current distribution. Reduced variation and a subset of haplotypes in glaciated regions suggest a founder effect associated with range expansion via long-distance seed dispersal. Our results do not support the “Driftless Area” scenario for the northern refugium, rather the data suggest a “Northeastern” refugium near the southernmost extent of the LGM.

Postglacial recolonization and Holocene diversification of Crocidura suaveolens (Mammalia, Soricidae) on the north-western fringe of the European continent

Phenotypic variation was characterized in 187 modern and archaeological specimens of the lesser white-toothed shrew (Crocidura suaveolens), obtained from both insular and continental European locations. Geometric morphometric methods were used to quantify variation in size and shape of the mandible. The phenotypic distance between populations, and the influence of several eco-geographical factors on the size and shape of the mandible in island populations, were assessed. Based on mandible shape divergence, the populations of C. suaveolens were clustered into continental, insular Atlantic and insular Mediterranean groups. Archaeological specimens from Molène Island, more than 3400 years old, display a mandible shape signal closer to that of the continental population than those of modern island populations. Conversely, the continental shape signals of the modern populations from Höedic and Sark suggest that these are relatively recent anthropogenic introductions. The populations of C. suaveolens from both the Atlantic and Mediterranean islands (except for Rouzic and Cyprus) show a significant increase in mandible size, compared to those from continental Europe. Significant phenotypic differences support the indigenous condition of C. suaveolens on most of the Atlantic islands, suggesting that the species arrived there before the separation of the Scilly Isles and Ushant from the continent due to the post-glacial rise in sea level. This provides an ante quem for its colonization of the north-western fringe of continental Europe, notwithstanding its absence from the region in the present day.