Extremely low levels of genetic diversity in the terrestrial orchid Epipactis thunbergii (Orchidaceae) in South Korea: implications for conservation

Levels of allozyme variation, population genetic structure, and fine-scale genetic structure (FSGS) of the rare, both sexually and clonally reproducing terrestrial orchid Epipactis thunbergii were examined for eight ( N  = 734) populations in a 20 × 20-km area in South Korea. Twenty-three putative allozyme loci resolved from 15 enzyme systems were used. Extremely low levels of allozyme variation were found within populations: the mean frequency of polymorphic loci was 3.8% [isocitrate dehydrogenase ( Idh-2 ) with two alleles was polymorphic across populations], the mean number of alleles per locus was 1.04, and the mean expected heterozygosity was 0.013. The overall fixation index was not significantly different from zero ( F _IS = 0.069), although the species is self-compatible. However, a significantly high degree of population differentiation was found between populations at Idh-2 ( F _ST = 0.388) in the studied area. Furthermore, spatial autocorrelation analyses revealed a significant FSGS (up to 3 m) within populations. These observations suggest that the main explanatory factors for the extremely low levels of genetic diversity and the shaping of the population genetic structure of E. thunbergii are genetic drift as a result of a small effective population size, a restricted gene flow, and the isolation of populations. Considering the current genetic structure of E. thunbergii , three guidelines are suggested for the development of conservation strategies for the species in South Korea: (1) protection of habitats of standing populations; (2) prohibition by law of any collection of E. thunbergii ; and (3) protection of nearby pollinator populations, given the fact that fruit set in natural habitats is very low.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 161–169.     

Contrasting levels of genetic diversity between the historically rare orchid Cypripedium japonicum and the historically common orchid Cypripedium macranthos in South Korea

Many terrestrial orchids are historically rare and occur in small, spatially isolated populations. Theory predicts that such species will harbour low levels of genetic variation within populations and will exhibit a high degree of population genetic divergence, primarily as a result of genetic drift. If the origin of the present‐day populations is relatively recent from the same genetically depauperate source population, a complete lack of genetic differentiation between conspecific populations is expected. If a terrestrial orchid was historically common with moderate or high levels of genetic diversity, but has experienced more recent anthropogenic disturbance as a result of over‐collection, it would still exhibit initial levels of genetic variation within populations and a low degree of genetic divergence between populations. To test these predictions, we examined the genetic diversity in six populations (N = 131) of the historically and currently rare Cypripedium japonicum and in four populations (N = 94) of the historically common but now rare C. macranthos from South Korea. Fourteen putative allozyme loci resolved from eight enzyme systems revealed no variation either within or among populations of C. japonicum, which supports the first prediction. In contrast, populations of C. macranthos harboured high levels of genetic variation (mean percentage of polymorphic loci %P = 46.7; mean expected heterozygosity H_e = 0.185) and exhibited a low degree of population genetic divergence (G_ST = 0.059), supporting the second prediction. The lack of genetic variation both within and among conspecific populations of C. japonicum may suggest that populations originated from the same genetically depauperate ancestral population. The high levels of genetic diversity maintained in populations of C. macranthos suggest that the collection‐mediated decrease in the number of individuals is still too recent for long‐term effects on genetic variation. Based on current demographic and genetic data, in situ and ex situ conservation strategies should be provided to preserve genetic variation and to ensure the long‐term survival of the two species in the Korean Peninsula. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 119–129.     

Contrasting levels of genetic diversity between the common, self-compatible Liparis kumokiri and rare, self-incompatible Liparis makinoana (Orchidaceae) in South Korea

Levels of allozyme variation and intrapopulation spatial genetic structure of the two terrestrial clonal orchids Liparis kumokiri , a self-compatible relatively common species, and L. makinoana , a self-incompatible rare species, were examined for 17 ( N  = 1875) and four ( N  = 425) populations, respectively, in South Korea. Populations of L. makinoana harboured high levels of genetic variation ( H _e = 0.319) across 15 loci. In contrast, L. kumokiri exhibited a complete lack of allozyme variation ( H _e = 0.000). Considering the lack of genetic variability, it is suggested that current populations of L. kumokiri in South Korea originated from a genetically depauperate ancestral population. For L. makinoana , a significant deficit of heterozygosity (mean F _IS = 0.198) was found in population samples excluding clonal ramets, suggesting that pollen dispersal is localized, generating biparental inbreeding. The significant fine-scale genetic structuring (≤ 2 m) found in a previous study, in addition to the moderate levels of population differentiation ( F _ST = 0.107) and the significant relationship between genetic and geographical distances ( r  = 0.680) found here, suggests a leptokurtic distribution of seed dispersal for L. makinoana . Although populations of L. makinoana harbour high levels of genetic variation, they are affected by a recent genetic bottleneck. This information suggests that genetic drift and limited gene flow could be the main evolutionary forces for speciation of a species-rich genus such as Liparis .  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 41–48.     

Phylogeography of the common goby, Pomatoschistus microps, with particular emphasis on the colonization of the Mediterranean and the North Sea

The phylogeographical patterns of a small marine fish, the common goby, Pomatoschistus microps, were assessed at 12 sites along the northeastern Atlantic coasts and the western Mediterranean Sea. A combination of two genetic markers was employed: cellulose acetate allozyme electrophoresis (CAGE) and sequence analysis of a 289 bp fragment of the mitochondrial locus cytochrome b. Both markers were congruent in revealing significant differences between samples (global FST = 0.247 for the allozymes and PhiST = 0.437 for the mitochondrial DNA data) and a pattern of isolation-by-distance. Phylogeographical analyses yielded a shallow branching structure with four groups. Three of those were confined to the Atlantic basin and showed a star-like pattern. The fourth group contained a central haplotype occurring at the edges of the species' distribution, accompanied by a few more rare variants, which were restricted to the Mediterranean Sea. A genetic break was observed around the British Isles, with distinct haplotypes dominating at either side of the English Channel. A significantly negative correlation between the degree of genetic diversity and latitude was recorded both for mitochondrial DNA (mtDNA) and allozymes in the Atlantic basin. Gene flow analysis suggested that recolonization of the North Sea and the coasts of western Scotland and Ireland may have taken place from a glacial refugium in the Southern Bight of the North Sea. These results are discussed in the perspective of possible postglacial migration routes of marine fish along the northeastern Atlantic coasts.     

Population genetic structure and diversity of the Apennine endemic stream frog, Rana italica--insights on the Pleistocene evolutionary history of the Italian peninsular biota

For most species in the Western Palaearctic region, southern Mediterranean peninsulas have been identified as major Quaternary refugia and hotspots of intraspecific diversity, and thus, as areas of particular relevance for the conservation of the evolutionary potential. We analysed the patterns of geographical variation among 26 populations of the Italian stream frog, using both nuclear (allozymes) and mitochondrial (partial cytochrome b sequences) markers. Phylogenetic, phylogeographical and population genetic analyses suggested that the species survived the last glacial–interglacial cycles in two distinct refugia, one restricted to the tip of the Calabrian peninsula, at the extreme south of the species' range, the other spanning from central Calabria to central Apennines and showing evidences for further population subdivision therein. Historical demographic tests suggested a significant population expansion from the latter, which most likely began around the last pleniglacial. This expansion would have led to the rapid colonization of the northern Apennines to the north, and to a secondary contact and population admixture with the population from the southern refugium in southern central Calabria. A comparison of the evolutionary history inferred for the Italian stream frog with the data emerging for other codistributed species suggests: (i) the generality of a multiple-refugia scenario for the Italian peninsula, (ii) the possible occurrence of at least one suture zone in southern Italy, and (iii) that for most species, this Pleistocene refugium is not only a hotspot, but also a melting pot of intraspecific genetic diversity. Finally, the conservation implications of these results are also briefly highlighted.     

Population genetic structure,genetic diversity,and natural history of the South American species of Nothofagus subgenus Lophozonia (Nothofagaceae) inferred from nuclear microsatellite data

The effect of glaciation on the levels and patterns of genetic variation has been well studied in the Northern Hemisphere. However, although glaciation has undoubtedly shaped the genetic structure of plants in the Southern Hemisphere, fewer studies have characterized the effect, and almost none of them using microsatellites. Particularly, complex patterns of genetic structure might be expected in areas such as the Andes, where both latitudinal and altitudinal glacial advance and retreat have molded modern plant communities. We therefore studied the population genetics of three closely related, hybridizing species of Nothofagus (N. obliqua, N. alpina, and N. glauca, all of subgenus Lophozonia; Nothofagaceae) from Chile. To estimate population genetic parameters and infer the influence of the last ice age on the spatial and genetic distribution of these species, we examined and analyzed genetic variability at seven polymorphic microsatellite DNA loci in 640 individuals from 40 populations covering most of the ranges of these species in Chile. Populations showed no significant inbreeding and exhibited relatively high levels of genetic diversity (H_E = 0.502–0.662) and slight, but significant, genetic structure (R_ST = 8.7–16.0%). However, in N. obliqua, the small amount of genetic structure was spatially organized into three well‐defined latitudinal groups. Our data may also suggest some introgression of N. alpina genes into N. obliqua in the northern populations. These results allowed us to reconstruct the influence of the last ice age on the genetic structure of these species, suggesting several centers of genetic diversity for N. obliqua and N. alpina, in agreement with the multiple refugia hypothesis.     

A comparison of genetic diversity levels in marine, freshwater, and anadromous fishes

Electrophoretic data were analysed from 49 species of freshwater fish, 57 species of marine fish, and seven anadromous species. For each species, at least 15 individuals had been assayed for at least 15 loci in two or more subpopulations. The results showed that while average total heterozygosity ( _T ) was approximately equal in freshwater and marine species (0·062 and 0·064 respectively), subpopulation heterozygosity ( _s ) was significantly less in the former group (0·046 and 0·059 respectively). Consequently the average degree of genetic subpopulation differentiation ( _ST ) was significantly greater for freshwater species (0·222 v. 0·062). On average, it is likely that marine subpopulations exchange between 10 and 100 times more migrants per generation than freshwater subpopulations, presumably because of the relative absence of barriers to dispersal in the marine environment. The reduced values of H_s in freshwater species are likely to reflect reduced effective subpopulation sizes relative to marine species. The few andromous species that have been analysed show intermediate levels of G_ST .     

Effects of current and historic habitat fragmentation on the genetic structure of the sand goby Pomatoschistus minutus (Osteichthys,Gobiidae)

Habitat fragmentation is a major force that will influence the evolution of a species and its distribution range. Pomatoschistus minutus, the sand goby, has a North Atlantic–Mediterranean distribution and shows various level of habitat fragmentation along its geographic repartition. The use of mitochondrial sequences of the cytochrome b (cyt b) gene and two co‐dominant sets of nuclear markers (introns and microsatellites) allowed us to describe the relationships between P. minutus populations belonging to several different geographical regions of Europe and to assess the structure of populations inhabiting the Golfe du Lion, along the French Mediterranean coast. The present study confirms that the taxon located in the Adriatic Sea (Venice) should be considered as a distinct species, separated approximately 1.75 Mya. The comparison of P. minutus between the Atlantic and western Mediterranean coasts using polymorphic co‐dominant markers revealed that they belong to two demographically independent units, and thus could be considered as well as distinct species, more recently separated (0.3 Mya). The Pleistocene glaciations seem therefore to have played an important role in the diversification of this complex. Finally, at a regional scale in the Golfe du Lion, P. minutus appears to form a single huge homogeneous population. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 175–198.     

Population genetic structure of the sidespot barb,Barbus neefi,from the north-eastern escarpment,South Africa

Allozyme analysis was used to determine patterns of genetic variation within and between populations of Barbus neefi. The products of 29 loci were analysed, with 17 loci being monomorphic in all populations. The genetic variability estimates compared well with values reported in the literature. The percentage of polymorphic loci (0.95 criterion) ranged from 0–20.69% and average expected heterozygosity from 0.004–0.069. Headstream populations generally revealed lower genetic variability than populations in low lying areas, which emphasizes the importance of conserving headstream populations. Fixed allele mobility differences were observed at the MPI-1 protein coding locus between the Selons River population and the other populations. The measures of genetic differentiation as assessed by F-statistics, the effective number of migrants per generation and Nei's unbiased genetic distance consistently separated the Selons River population from the rest. Nevertheless, these estimates all fell within the range considered for conspecific populations. There was also a clear genetic division between populations from north and south of the Olifants River. The three populations from the Dorps, Spekboom and Blyde Rivers (Limpopo River system) and the population from the Crocodile River (Incomati River system) showed negligible genetic differentiation. Human-assisted transfer of populations may be responsible for this close similarity.     

Putative glacial refugia of Cedrus atlantica deduced from Quaternary pollen records and modern genetic diversity

Aim To investigate the impact of past environmental changes on Cedrus atlantica and its current genetic diversity, and to predict its future distribution. Location Morocco, Algeria and Tunisia. Methods Eleven fossil pollen records from these three countries were used to locate putative glacial refugia and to reconstruct past climate changes. A mechanistic vegetation distribution model was used to simulate the distribution of C. atlantica in the year 2100. In addition, a genetic survey was carried out on modern Moroccan C. atlantica. Results Pollen records indicate that Cedrus was present during the last glacial period, probably in scattered refugia, in Tunisia, Algeria and Morocco. In the Tunisian and Algerian sites, cedar expanded during the late glacial and the early Holocene, then disappeared after c. 8000 yr bp . Reconstructed mean annual precipitation and January temperature show that the last glacial period in Morocco was cooler by 10–15°C and drier by c. 300–400 mm year^?1 than the climate today. Modern chloroplast microsatellites of 15 C. atlantica populations in Morocco confirm the presence of multiple refugia and indicate that cedar recolonized the Moroccan mountains fairly recently. Model simulation indicates that by the year 2100 the potential distribution of C. atlantica will be much restricted with a potential survival area located in the High Atlas. Main conclusions Environmental changes in northern Africa since the last glacial period have had an impact on the geographical distribution of C. atlantica and on its modern genetic diversity. It is possible that by the end of this century C. atlantica may be unable to survive in its present‐day locations. To preserve the species, we suggest that seedlings from modern C. atlantica populations located in the High Atlas mountains, where a high genetic diversity is found, be transplanted into the western High Atlas.     

Post-pleistocene demographic history of the North Atlantic endemic Irish moss Chondrus crispus: glacial survival, spatial expansion and gene flow

Range expansions and gene flow as micro-evolutionary processes played a leading role in the population demographic history of marine organisms. Herein, we sequenced partial mtDNA Cox1 gene from 26 assigned geographical populations to understand how Irish moss (Chondrus crispus) responded to severe climatic oscillations during the Pleistocene glaciations and contemporary forces such as gene flow. Phylogeographic patterns indicated that haplotype frequency distributions were strongly skewed, with nearly half found only in single samples and thus restricted to a single population. Analysis of molecular variance revealed that most of the variation was within populations with no significant genetic structuring on either side of the Atlantic. Demographic analyses indicated that ISI (Irish Sea and Ireland) and NS (the North Sea) areas experienced a slight trend of increase in population size over time, whereas EC (the English Channel) area experienced expansion beginning approximately 170,000-360,000 BP. The observed complex genetic pattern of C. crispus is consistent with a scenario of multiple unrelated founding events by survival of this species in at least three putative Pleistocene refugia along the European coastline, and subsequent trans-Atlantic dispersal combined with contiguous northward population expansion predating the LGM and geographically gene flow.     

Communally breeding Bechstein's bats have a stable social system that is independent from the postglacial history and location of the populations

Investigating macro-geographical genetic structures of animal populations is crucial to reconstruct population histories and to identify significant units for conservation. This approach may also provide information about the intraspecific flexibility of social systems. We investigated the history and current structure of a large number of populations in the communally breeding Bechstein's bat ( Myotis bechsteinii ). Our aim was to understand which factors shape the species' social system over a large ecological and geographical range. Using sequence data from one coding and one noncoding mitochondrial DNA region, we identified the Balkan Peninsula as the main and probably only glacial refugium of the species in Europe. Sequence data also suggest the presence of a cryptic taxon in the Caucasus and Anatolia. In a second step, we used seven autosomal and two mitochondrial microsatellite loci to compare population structures inside and outside of the Balkan glacial refugium. Central European and Balkan populations both were more strongly differentiated for mitochondrial DNA than for nuclear DNA, had higher genetic diversities and lower levels of relatedness at swarming (mating) sites than in maternity (breeding) colonies, and showed more differentiation between colonies than between swarming sites. All these suggest that populations are shaped by strong female philopatry, male dispersal, and outbreeding throughout their European range. We conclude that Bechstein's bats have a stable social system that is independent from the postglacial history and location of the populations. Our findings have implications for the understanding of the benefits of sociality in female Bechstein's bats and for the conservation of this endangered species.     

Genetic diversity and phylogeography of the Apennine yellow-bellied toad Bombina pachypus, with implications for conservation

Genetic variation was investigated in 17 populations of the Italian endemic Apennine yellow-bellied toad using both mitochondrial (598 bp of the cytochrome b gene) and nuclear (21 allozyme loci) markers. Populations from central Calabria (southern Italy) showed the highest levels of intrapopulation genetic variation, whereas samples located north of this region were nearly lacking in variation. This appears to be a typical pattern of 'southern richness and northern purity', usually attributed to the prolonged population stability within southern refugia coupled with the loss of variation during postglacial northward expansion. However, the overall pattern of genetic variation observed has a strong geographical component, suggesting two Calabrian plains, Catanzaro and Crati-Sibari, as historical barriers to dispersal separating three population groups. These findings cannot be explained by the prolonged stability of southern populations alone, and suggest that the southern richness has been at least in part shaped by allopatric differentiation within the refugial range, followed by intermixing of previously differentiated lineages. From a conservation standpoint, Calabria is the major genetic diversity reservoir for this species, thus deserving particular conservation efforts. Furthermore, although the low intrapopulation genetic variation outside Calabria appears to be of clear historical origin, evidence of a current reduction of gene flow suggests that human disturbance has also played a part, particularly in the anthropogenic impacted Volturno river drainage basin.     

High levels of genetic diversity in marginal populations of the marsh orchid Dactylorhiza majalis subsp. majalis

Because of harsh conditions, suboptimal habitat quality and poor connectivity to other populations, plant populations at the margin of a distribution are expected to be less genetically diverse, but to be more divergent from each other than populations in the centre of a distribution. In northern Europe, northern marginal populations may also be younger than populations further to the south, and may have had less time to accumulate genetic diversity by mutation and gene flow. However, orchids have very small seeds, which are easily dispersed long distances by wind, and orchids are therefore expected to show less differentiation between marginal and central populations than other groups of seed plants. Here, we analysed whether Scandinavian populations of the tetraploid marsh orchid Dactylorhiza majalis subsp. majalis differ from central European populations in genetic diversity patterns. A total of 220 plants from eight central European and ten Scandinavian populations was examined for variation at five nuclear microsatellite loci, nuclear ITS and 13 polymorphic sites in noncoding regions of the plastid genome. The total genetic diversity was slightly lower in Scandinavia than in central Europe, both in plastid and nuclear markers, but the differences were small. Also, the Scandinavian populations were less diverse and somewhat more strongly differentiated from each other than the central European ones. Dactylorhiza majalis subsp. majalis has apparently colonized Scandinavia on multiple independent occasions and from different source areas in the south. Seed flow between Scandinavian populations has still not fully erased the patterns imprinted by early colonization. Our results suggest that marginal populations of orchids may be as important as central ones in preserving genetic diversity through Pleistocene glacial cycles. We also predict that orchids with their light seeds are better adapted than many other plants to respond to future climate changes by dispersing into new suitable areas.     

河南宝天曼不同林龄与林型森林土壤的细菌群落结构与多样性

采用高通量16S rRNA标签测序法,比较了地处北亚热带与暖温带过渡带的宝天曼自然保护区不同林龄与林分类型的土壤细菌群落结构及多样性.结果表明： 宝天曼森林土壤细菌以变形菌门(29%)、酸杆菌门(18.5%)、疣微菌门(10%)等为主,共检测到60门1209属,优势属主要有疣微菌门的DA101(6.3%)、酸杆菌门的Acidobacteria 2(5.9%)和Candidatus Solibacter(2.9%)、泉古菌门的Candidatus Nitrososphaera(2.6%)等.不同林龄和林分类型土壤分别具有特有的种属组成及高丰度和低丰度种属.林龄与林分类型都对土壤微生物群落结构影响显著,且林分类型的影响大于林龄.80年林龄的锐齿栎土壤菌群多样性在不同林龄和林分类型中均最低.pH、土壤全氮、有机碳等是不同林龄及林分类型下土壤菌群结构变化的重要影响因子.     

Rangewide phylogeography in the greater horseshoe bat inferred from microsatellites: implications for population history, taxonomy and conservation

The distribution of genetic variability across a species' range can provide valuable insights into colonization history. To assess the relative importance of European and Asian refugia in shaping current levels of genetic variation in the greater horseshoe bats, we applied a microsatellite-based approach to data collected from 56 localities ranging from the UK to Japan. A decline in allelic richness from west Asia to the UK and analyses of F(ST) both imply a northwestward colonization across Europe. However, sharp discontinuities in gene frequencies within Europe and between the Balkans and west Asia (Syria/Russia) are consistent with suture zones following expansion from multiple refugia, and a lack of recent gene flow from Asia Minor. Together, these results suggest European populations originated from west Asia in the ancient past, and experienced a more recent range expansion since the Last Glacial Maximum. Current populations in central Europe appear to originate from the Balkans and those from west Europe from either Iberia and/or Italy. Comparisons of R(ST )and F(ST) suggest that stepwise mutation has contributed to differentiation between island and continental populations (France/UK and China/Japan) and also among distant samples. However, pairwise R(ST) values between distant populations appear to be unreliable, probably due to size homoplasy. Our findings also highlight two priorities for conservation. First, stronger genetic subdivision within the UK than across 4000 km of continental Eurasia is most likely the result of population fragmentation and highlights the need to maintain gene flow in this species. Second, deep splits within China and between Europe and China are indicative of cryptic taxonomic divisions which need further investigation.     

Gene flow from multiple sources maintains high genetic diversity and stable population history of Common Moorhen Gallinula chloropus in China

In this study, we used mitochondrial control sequences and microsatellite data from 231 Common Moorhen Gallinula chloropus individuals sampled from 19 sites in China to analyse their genetic structure and evolutionary history. High genetic diversity was found for all populations, although microsatellite analysis showed that the genetic diversity in non‐migratory populations was significantly higher than in migratory populations. High gene flow occurred between neighbouring populations, although long‐distance gene flow also occurred. The Huazhong population was the single greatest genetic source for other populations. High gene flow probably led to the shallow genetic structure that we observed. Demographic expansion was found in migratory populations, non‐migratory populations and with all individuals combined. The expansion time for all populations combined was estimated to be 221 000 years ago. The Common Moorhen population grew rapidly during the interglacial before the last glacial maximum (LGM), then remained generally stable from the LGM to the present.     

Population history and gene dispersal inferred from spatial genetic structure of a Central African timber tree,Distemonanthus benthamianus (Caesalpinioideae)

African rainforests have undergone major distribution range shifts during the Quaternary, but few studies have investigated their impact on the genetic diversity of plant species and we lack knowledge on the extent of gene flow to predict how plant species can cope with such environmental changes. Analysis of the spatial genetic structure (SGS) of a species is an effective method to determine major directions of the demographic history of its populations and to estimate the extent of gene dispersal. This study characterises the SGS of an African tropical timber tree species, Distemonanthus benthamianus, at various spatial scales in Cameroon and Gabon. Displaying a large continuous distribution in the Lower Guinea domain, this is a model species to detect signs of past population fragmentation and recolonization, and to estimate the extent of gene dispersal. Ten microsatellite loci were used to genotype 295 adult trees sampled from eight populations. Three clearly differentiated gene pools were resolved at this regional scale and could be linked to the biogeographical history of the region, rather than to physical barriers to gene flow. A comparison with the distribution of gene pools observed for two other tree species living in the same region invalidates the basic assumption that all species share the same Quaternary refuges and recolonization pathways. In four populations, significant and similar patterns of SGS were detected. Indirect estimates of gene dispersal distances (sigma) obtained for three populations ranged from 400 to 1200 m, whereas neighbourhood size estimates ranged from 50 to 110.     

Pleistocene glaciations and contemporary genetic diversity in a Beringian fish,the broad whitefish,Coregonus nasus (Pallas): inferences from microsatellite DNA variation

The contemporary distribution of genetic variation within and among high latitude populations cannot be fully understood without taking into consideration how species responded to the impacts of Pleistocene glaciations. Broad whitefish, Coregonus nasus, a species endemic to northwest North America and the Arctic coast of Russia, was undoubtedly impacted by such events because its geographic distribution suggests that it survived solely within the Beringian refuge from where it dispersed post‐glacially to achieve its current range. We used microsatellite DNA to investigate the role of glaciations in promoting intraspecific genetic variation in broad whitefish (N = 14 localities, 664 fish) throughout their North American range and in one Russian sample. Broad whitefish exhibited relatively high intrapopulation variation (average of 11.7 alleles per locus, average H_E = 0.61) and moderate levels of interpopulation divergence (overall F_ST = 0.10). The main regions assayed in our study (Russia, Alaska, Mackenzie River and Travaillant Lake systems) were genetically differentiated from each other and there were declines in genetic diversity with distance from putative refugia. Additionally, Mackenzie River system populations showed less developed and more variable patterns of isolation‐by‐distance than populations occupying former Alaskan portions of Beringia. Finally, our data suggest that broad whitefish dispersed from Beringia using coastal environments and opportunistically via headwater stream connections that once existed between Yukon and Mackenzie River drainages. Our results illustrate the importance of history (e.g. glaciation) and contemporary dispersal ecology in shaping the current genetic population structure of Arctic faunas.