The genetic pattern of population threat and loss: a case study of butterflies

Recent decreases in biodiversity in Europe are commonly thought to be due to land use and climate change. However, the genetic diversity of populations is also seen as one essential factor for their fitness. Genetic diversity in species across the continent of Europe has been recognized as being in part a consequence of ice age isolation in southern refugia and postglacial colonization northwards, and these phylogeographical patterns may themselves affect the adaptability of populations. Recent work on butterfly species with different refugia, colonization paths and genetic structures allows this idea to be examined. The 'chalk-hill blue' pattern is one of decreasing genetic diversity from south to north, whereas the 'woodland ringlet' pattern shows greater genetic diversity in eastern than in western lineages. Comparison of population demographic trends in species with these biogeographical patterns reveals higher rates of decrease with lower genetic diversity. This indicates reduced adaptability due to genetic impoverishment as a result of glacial and postglacial range changes. Analysis of phylogeographical pattern may be a useful guide to interpreting demographic trends and in conservation planning.     

Genetic structure and diversity of a rare woodland bat, <Emphasis Type="Italic">Myotis bechsteinii</Emphasis>: comparison of continental Europe and Britain

The Bechstein’s bat (Myotis bechsteinii) is a rare sedentary bat considered to be highly reliant on the presence of ancient woodland. Understanding the genetic connectivity and population structure of such elusive mammals is important for assessing their conservation status. In this study, we report the genetic diversity and structure of M. bechsteinii across Britain and Europe. Assessments were made using 14 microsatellite markers and a 747 bp region of the mitochondrial cytochrome b gene. Nuclear DNA (microsatellites) showed high levels of genetic diversity and little inbreeding across the species range, though genetic diversity was slightly lower in Britain than in mainland Europe. Bayesian and spatial PCA analysis showed a clear separation between the British and European sites. Within Europe, the Italian population south of the Alps was isolated from the other sites. In Britain, there was genetic structuring between the northern and southern part of the geographical range. Despite there being little genetic divergence in mitochondrial DNA (mtDNA) sequences throughout most of Europe, the mtDNA patterns in Britain confirmed this separation of northern and southern populations. Such genetic structuring within Britain—in the absence of any obvious physical barriers—suggests that other factors such as land-use may limit gene-flow.     

Phylogeography of the white-tailed eagle, a generalist with large dispersal capacity

Aim Late Pleistocene glacial changes had a major impact on many boreal and temperate taxa, and this impact can still be detected in the present‐day phylogeographic structure of these taxa. However, only minor effects are expected in species with generalist habitat requirements and high dispersal capability. One such species is the white‐tailed eagle, Haliaeetus albicilla, and we therefore tested for the expected weak population structure at a continental level in this species. This also allowed us to describe phylogeographic patterns, and to deduce Ice Age refugia and patterns of postglacial recolonization of Eurasia. Location Breeding populations from the easternmost Nearctic (Greenland) and across the Palaearctic (Iceland, continental Europe, central and eastern Asia, and Japan). Methods Sequencing of a 500 base‐pair fragment of the mitochondrial DNA control region in 237 samples from throughout the distribution range. Results Our analysis revealed pronounced phylogeographic structure. Overall, low genetic variability was observed across the entire range. Haplotypes clustered in two distinct haplogroups with a predominantly eastern or western distribution, and extensive overlap in Europe. These two major lineages diverged during the late Pleistocene. The eastern haplogroup showed a pattern of rapid population expansion and colonization of Eurasia around the end of the Pleistocene. The western haplogroup had lower diversity and was absent from the populations in eastern Asia. These results suggest survival during the last glaciation in two refugia, probably located in central and western Eurasia, followed by postglacial population expansion and admixture. Relatively high genetic diversity was observed in northern regions that were ice‐covered during the last glacial maximum. This, and phylogenetic relationships between haplotypes encountered in the north, indicates substantial population expansion at high latitudes. Areas of glacial meltwater runoff and proglacial lakes could have provided suitable habitats for such population growth. Main conclusions This study shows that glacial climate fluctuations had a substantial impact on white‐tailed eagles, both in terms of distribution and demography. These results suggest that even species with large dispersal capabilities and relatively broad habitat requirements were strongly affected by the Pleistocene climatic shifts.     

Genetic variation of Eryngium campestre L. (Apiaceae) in Central Europe

In Germany, Eryngium campestre is restricted to dry habitats along the rivers Rhine and Elbe and to a few areas in Central Germany. This distribution pattern is usually regarded as a typical pattern of postglacial immigration. In the present study, we investigated whether these two geographically distinct distribution areas are genetically differentiated and whether conclusions can be drawn regarding colonization history. To analyse the phylogeographic structure of E. campestre in Central Europe, 278 individuals from 29 populations within Germany and from further reference populations within Europe were analysed. We applied amplified fragment length polymorphisms to examine their genetic relatedness. Our analyses revealed three groups: a Mediterranean group additionally including two Rhine populations; a Rhine–Main group which further includes the westernmost population from the central German dry area; and one group which includes all eastern populations. Our results show that the two geographically distinct areas are genetically differentiated. As genetic diversity within the Elbe populations is very low, we conclude that this area, which was strongly affected through the late glacial maximum, was colonized relatively recently. High genetic diversity in the Rhine populations indicates a contact zone where lineages of different origin met. This would imply that today's patterns of genetic variation were caused through glacial range contractions and expansions. The present study is one of the first studies that deal with the postglacial distribution pattern of a dry grassland plant species in Central Europe and the results suggest that a survival of E. campestre at least during the Dryas cold stage might be possible.     

Ice-age isolation,postglacial hybridization and recent population bottlenecks shape the genetic structure of Meum athamanticum in Central Europe

Phylogeographic analyses can help to reveal the refugial structure of plants during and after the ice ages, but the detailed history of regional refugial isolation and differentiation in Central Europe is still poorly understood. A recent study of Meum athamanticum in its total range of occurrences revealed persistence of this temperate montane plant species in Central Europe north of the Alps, without going into details. We therefore aimed to study differentiation and migration processes of this plant species in more detail throughout Central Europe. We used high resolution amplified fragment length polymorphisms (AFLP) markers and analyzed 210 plant individuals of 14 Central European populations with three pairs of primer combinations (128 loci, 111 of which polymorphic). The data show genetic differentiation and varying levels of molecular diversity within populations and groups of populations. Altogether, the studied populations did not show a gradient in molecular variation along presumptive postglacial migration routes across Central Europe. Rather, they reveal a genetic division into seven major groups. Four of them are characterised by high genetic diversity, private fragments and higher than average number of rare and sparse fragments, leading to the assumption that they are descendants of independent populations which survived in glacial refugia. In combination with information from paleoclimate and paleovegetation, it is likely that microclimatically favoured habitats at (i) the eastern flank of the Black Forest, (ii) the southern margin of the Cologne basin, (iii) the foothills of the Erzgebirge, and (iv) the foothills of the Jura Mountains acted as sources for the postglacial recolonisation of this species to the other mountains of Central Europe. As some of the populations analysed show intermixed gene-pools (i.e. including genetic information from different groups) and partly have exceptionally high genetic diversity, but no private and only relatively few rare or sparse fragments, they might represent contact zones. On the other hand, genetic pauperization and isolation of two other populations in connection with extremely small population sizes and unfavourable habitat conditions seem to reflect recent bottlenecks. Consequently, the genetic structure of M. athamanticum in Central Europe is shaped by (i) extra-Mediterranean glacial refugia in situ, (ii) following postglacial hybridization along emerging contact zones and (iii) genetic bottlenecks in thereafter isolated small populations. All results provide evidences for small scale migration of the species between Central European valleys and surrounding highlands. Therefore, our study provides molecular evidence for both climate dependent wide ranging periglacial tabula rasa, but some small refugia in locally buffered areas. We hereby show that the environmental heterogeneity of cold stage landscapes in Central Europe is generally underestimated.     

Genetic consequences of glacial survival and postglacial colonization in Norway spruce: combined analysis of mitochondrial DNA and fossil pollen

Norway spruce (Picea abies [L.] Karst.) is a broadly distributed European conifer tree whose history has been intensively studied by means of fossil records to infer the location of full‐glacial refugia and the main routes of postglacial colonization. Here we use recently compiled fossil pollen data as a template to examine how past demographic events have influenced the species’ modern genetic diversity. Variation was assessed in the mitochondrial nad1 gene containing two minisatellite regions. Among the 369 populations (4876 trees) assayed, 28 mitochondrial variants were identified. The patterns of population subdivision superimposed on interpolated fossil pollen distributions indicate that survival in separate refugia and postglacial colonization has led to significant structuring of genetic variation in the southern range of the species. The populations in the northern range, on the other hand, showed a shallow genetic structure consistent with the fossil pollen data, suggesting that the vast northern range was colonized from a single refugium. Although the genetic diversity decreased away from the putative refugia, there were large differences between different colonization routes. In the Alps, the diversity decreased over short distances, probably as a result of population bottlenecks caused by the presence of competing tree species. In northern Europe, the diversity was maintained across large areas, corroborating fossil pollen data in suggesting that colonization took place at high population densities. The genetic diversity increased north of the Carpathians, probably as a result of admixture of expanding populations from two separate refugia.     

Phylogeography of European moose (Alces alces) based on contemporary mtDNA data and archaeological records

Phylogeography can help to determine LGM refugia and postglacial migration routes. However, the locations of LGM refugial areas in eastern Europe are not clear. Moose (Alces alces) is presently a common species in central and north-eastern Europe, but there are no studies showing its phylogenetic pattern and genetic diversity across its whole continuous range. Moose never became extinct in the eastern part of its range, and the eastern mtDNA lineage has the largest effective population size. The present study shows the phylogeographic pattern and genetic diversity of European moose and compares the results of mtDNA analyses with the archaeological record of the species to identify its LGM refugia and postglacial migration routes. I combined the mtDNA control region sequences obtained in all studies of moose in Europe and western Asia. The genetic data were then compared with the archaeological records of the species dated to the LGM. I found that the European moose lineage inhabits Europe and western Asia. It is composed of two clades: the eastern and the central-western, consisting of a total of six discrete haplogroups. The most complex, the eastern clade, has the largest range. Some of the haplogroups have narrow or scattered distributions and two are common in almost the whole range. Genetic diversity hotspots were detected in contact zones of different mtDNA haplogroups rather than in the LGM refugial areas of moose. Archaeological records dated to the LGM were found in several localities in central, southern and eastern Europe as well as in western Asia. The range of the moose during the LGM was much larger than previously thought. The eastern clade survived the LGM in western Siberia, the Ural Mountains and Russian plain. LGM refugia of moose were also located in the Caucasus, Carpathians, Balkans and northern Italy.     

Drainage-independent genetic structure and high genetic diversity of endangered freshwater pearl mussels (<Emphasis Type="Italic">Margaritifera margaritifera</Emphasis>) in northern Europe

Freshwater pearl mussels (Margaritifera margaritifera) are among the most critically threatened bivalve molluscs worldwide. An understanding of spatial patterns of genetic diversity is crucial for the development of integrative conservation strategies. We used microsatellites to study the genetic diversity and differentiation of 14 populations of M. margaritifera in central Sweden, an area which was described as a major secondary contact zone in postglacial colonisation for other species. Genetic diversity of Swedish pearl mussel populations was much greater than in central and southern Europe but similar to the genetic diversity observed in the northeastern portion of their European range. Genetic differentiation among populations was pronounced but to a large extent independent from present-day drainage systems. The complex patterns of genetic diversity and differentiation in pearl mussel seem to be strongly influenced by the species’ high degree of specialisation and extraordinary life history strategy which involves facultative hermaphrodism and an obligatory encystment stage on a host fish. Genetic drift effects and anthropogenic disturbances resulting in reduction of population size and loss of connectivity are less pronounced in northern pearl mussel populations compared to those in central and southern Europe.     

Phylogeography reveals latitudinal population structure in the common herb Plantago coronopus

The increase in gene diversity from high to low latitudes is a widely recognized biogeographical pattern, often shaped by differential effects of Late Quaternary climatic changes. Here, we evaluate the effects of Pleistocene climatic changes from northern Europe to North Africa and their implications on the population differentiation of the widespread, short‐lived herb Plantago coronopus. We used amplified fragment length polymorphism to investigate the population structure and phylogeography of P. coronopus in 273 individuals from 29 populations covering its complete latitudinal range. Although Bayesian clustering, principal coordinates analysis and a consensus UPGMA tree were not fully congruent, two well‐supported clades, associated with distinct latitudinal zones (northern Europe and the Mediterranean region), were revealed as a general pattern. Moreover, populations from the western Atlantic edge and, to a lesser extent, the central Mediterranean region exhibited signs of admixture, suggesting secondary contacts. The admixed populations in the western Atlantic and central Mediterranean are geographically intermediate between the northern and southern lineages. The northernmost lineage exhibited low genetic diversity, a clear sign of a recent colonization. In contrast, populations from the southernmost part of the range showed the highest level of genetic diversity, indicating possible refugia for the species during the Quaternary ice ages. Overall, our study allows spatial structure of the genetic variation of a widespread herb across its latitudinal range to be disentangled and provides insights into how past climatic history influences present genetic patterns. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 618–634.     

Nuclear microsatellites reveal contrasting patterns of genetic structure between western and southeastern European populations of the common ash (Fraxinus excelsior L.)

To determine extant patterns of population genetic structure in common ash and gain insight into postglacial recolonization processes, we applied multilocus-based Bayesian approaches to data from 36 European populations genotyped at five nuclear microsatellite loci. We identified two contrasting patterns in terms of population genetic structure: (1) a large area from the British Isles to Lithuania throughout central Europe constituted effectively a single deme, whereas (2) strong genetic differentiation occurred over short distances in Sweden and southeastern Europe. Concomitant geographical variation was observed in estimates of allelic richness and genetic diversity, which were lowest in populations from southeastern Europe, that is, in regions close to putative ice age refuges, but high in western and central Europe, that is, in more recently recolonized areas. We suggest that in southeastern Europe, restricted postglacial gene flow caused by a rapid expansion of refuge populations in a mountainous topography is responsible for the observed strong genetic structure. In contrast, admixture of previously differentiated gene pools and high gene flow at the onset of postglacial recolonization of western and central Europe would have homogenized the genetic structure and raised the levels of genetic diversity above values in the refuges.     

Spatial patterns of genetic diversity across European subspecies of the mountain hare, Lepus timidus L

Fossil evidence shows that populations of species that currently inhabit arctic and boreal regions were not isolated in refugia during glacial periods, but instead maintained populations across large areas of central Europe. These species commonly display little reduction in genetic diversity in northern areas of their range, in contrast to many temperate species. The mountain hare currently inhabits both temperate and arctic-boreal regions. We used nuclear microsatellite and mtDNA sequence data to examine population structure and alternate phylogeographic hypotheses for the mountain hare, that is, temperate type (lower genetic diversity in northern areas) and arctic-boreal type (high northern genetic diversity). Both data sets revealed concordant patterns. Highest allelic richness, expected heterozygosity and mtDNA haplotype diversity were identified in the most northerly subspecies, indicating that this species more closely maps to phylogeographic patterns observed in arctic-boreal rather than temperate species. With regard to population structure, the Alpine and Fennoscandian subspecies were most genetically similar (F(ST) approximately 0.1). These subspecies also clustered together on the mtDNA tree and were assigned with highest likelihood to a common Bayesian cluster. This is consistent with fossil evidence for intermediate populations in the central European plain, persisting well into the postglacial period. In contrast, the geographically close Scottish and Irish populations occupied separate Bayesian clusters, distinct clades on the mtDNA maximum likelihood tree and were genetically divergent from each other (F(ST) > 0.4) indicating the influence of genetic drift, long isolation (possibly dating from the late glacial era) and/or separate postglacial colonisation routes.     

Chloroplast DNA variation,postglacial recolonization and hybridization in hazel,Corylus avellana

To unravel the postglacial migration history of hazel, Corylus avellana, the genetic variation at two types of chloroplast DNA markers, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and microsatellites, was assessed in 26 natural hazel populations distributed across the range of C. avellana. In addition a sequence of 2468 base pairs, which contains the matK gene, was analysed in seven individuals. Very little variation was detected overall [hT:PCR-RFLP= 0.091, hT:microsatellite= 0.423, pi (nucleotide diversity) = 0.00093] but the microsatellite markers, which have the highest levels of variation, show a clear geographical structure that divides Europe into two areas: (i) Italy and the Balkans, on one hand and (ii) the rest of Europe, on the other hand. These data exclude Italy and the Balkans as possible origins of the postglacial recolonization but cannot unambiguously show which other area is the origin, since the genetic data does not indicate the direction of spread. If we take the pollen record into account, the most likely scenario would be an expansion from southwestern France into most of Europe except Italy and the Balkans, and then a local expansion in the latter area. The two main haplotypes identified with both PCR-RFLP and sequencing, A and B, were found not only in C. avellana but also in other European Corylus species and cultivars. Haplotype A, which is dominating all investigated natural populations of C. avellana, is also found in the European tree hazel (C. colurna) and haplotype B, which is rare in C. avellana, has been identified in the filbert (C. maxima) and C. avellana cultivars. This pattern seems to indicate a history of past hybridization among the European Corylus species and cultivars.     

Genetic consequences of climatic oscillations in the Quaternary

An appreciation of the scale and frequency of climatic oscillations in the past few million years is modifying our views on how evolution proceeds. Such major events caused extinction and repeated changes in the ranges of those taxa that survived. Their spatial effects depend on latitude and topography, with extensive extinction and recolonization in higher latitudes and altitudinal shifts and complex refugia nearer the tropics. The associated population dynamics varied with life history and geography, and the present genetic constitution of the populations and species carry attenuated signals of these past dynamics. Phylogeographic studies with DNA have burgeoned recently and studies are reviewed from the arctic, temperate and tropical regions, seeking commonalities of cause in the resulting genetic patterns. Arctic species show distinct shallow genetic clades with common geographical boundaries. Thus Beringia is distinct phylogeographically, but its role as a refugial source is complex. Arctic taxa do not show the common genetic pattern of southern richness and northern purity in north-temperate species. Temperate refugial regions in Europe and North America show relatively deep DNA divergence for many taxa, indicating their presence over several Ice Ages, and suggesting a mode of speciation by repeated allopatry. DNA evidence indicates temperate species in Europe had different patterns of postglacial colonization across the same area and different ones in previous oscillations, whereas the northwest region of North America was colonized from the north, east and south. Tropical montane regions contain deeply diverged lineages, often in a relatively small geographical area, suggesting their survival there from the Pliocene. Our poor understanding of refugial biodiversity would benefit from further combined fossil and genetic studies.     

Higher genetic diversity in recolonized areas than in refugia of Alnus glutinosa triggered by continent‐wide lineage admixture

Genetic admixture is supposed to be an important trigger of species expansions because it can create the potential for selection of genotypes suitable for new climatic conditions. Up until now, however, no continent‐wide population genetic study has performed a detailed reconstruction of admixture events during natural species expansions. To fill this gap, we analysed the postglacial history of Alnus glutinosa, a keystone species of European swamp habitats, across its entire distribution range using two molecular markers, cpDNA and nuclear microsatellites. CpDNA revealed multiple southern refugia located in the Iberian, Apennine, Balkan and Anatolian Peninsulas, Corsica and North Africa. Analysis of microsatellites variation revealed three main directions of postglacial expansion: (i) from the northern part of the Iberian Peninsula to Western and Central Europe and subsequently to the British Isles, (ii) from the Apennine Peninsula to the Alps and (iii) from the eastern part of the Balkan Peninsula to the Carpathians followed by expansion towards the Northern European plains. This challenges the classical paradigm that most European populations originated from refugial areas in the Carpathians. It has been shown that colonizing lineages have met several times and formed secondary contact zones with unexpectedly high population genetic diversity in Central Europe and Scandinavia. On the contrary, limited genetic admixture in southern refugial areas of A. glutinosa renders rear‐edge populations in the Mediterranean region more vulnerable to extinction due to climate change.     

Phylogeography and genetic diversity of the red squirrel (Sciurus vulgaris) in China: Implications for the species' postglacial expansion history

The geographical distribution of Sciurus vulgaris spans much of the Palearctic from western Europe and the UK eastward to the pacific coast of East Asia. S. vulgaris occurs in China only in the far northwest and the northeast. Understanding of the species’ postglacial expansion history in East Asia has been limited by the paucity of molecular data. In this study, we used partial D-loop and cytochrome b gene sequences to assess mitochondrial DNA variation in S. vulgaris in China. Our objectives were to (1) determine phylogeographical patterns of S. vulgaris in China; (2) understand the species’ postglacial expansion history in this region; and (3) quantify genetic diversity levels within S. vulgaris populations in China. We identified a supported phylogenetic group in S. vulgaris from China, and found no tendency for haplotypes to cluster by geographic region. Our analysis of S. vulgaris from China and other regions supports the hypothesis that the Calabria region of southern Italy is a glacial refugium for the species. We tentatively propose a postglacial expansion pattern for the squirrels: migrating from Calabria via Central and Eastern Europe to Russia and from there to China, and firstly to the northwest and then to northeast in China. We found high levels of genetic diversity in S. vulgaris populations across China as a whole, and discussed its influential factors.     

Strong genetic impoverishment from the centre of distribution in southern Europe to peripheral Baltic and isolated Scandinavian populations of the pearly heath butterfly

Aim Climatic changes and fluctuations in the past have strongly influenced the distribution of animal and plant species. Such fluctuations are also reflected in the patterns of genetic diversity on both local and global scales. The genetic pattern of the pearly heath butterfly, Coenonympha arcania, was used to evaluate the genetic differentiation of isolated (in north‐western Europe), peripheral (in north‐eastern Europe) and central (in southern Europe) populations in the context of post‐glacial distributional changes of the species. Location Europe (Sweden, Germany, the Baltic states, Italy, Slovenia, Hungary, Romania, Bulgaria). Thus, samples were collected from large parts of the species’ distribution representing the three categories mentioned above. Methods We analysed 18 loci of 569 individuals from 28 populations by allozyme electrophoresis. We used both individual‐based and population‐based analyses, including F‐statistics, various clustering methods and Markov chain Monte Carlo simulations. Results All loci, except Fum, were polymorphic. The mean F_ST for all samples was 0.18. The mean genetic distance among populations was 0.046. Two major genetic lineages were distinguished. Populations from the centre of the distributional range in southern Europe and the northern periphery of the distributional range differed significantly in their level of genetic variability. The central populations of south‐eastern Europe showed high levels of genetic diversity and no differentiation among populations. Main conclusions Most probably the two major genetic lineages evolved during glacial isolation in two disjunct Mediterranean refugia. The lack of genetic differentiation across south‐eastern Europe implies a continuous Würm ice age distribution in this area, thus supporting the functional existence of steppe forests throughout this region. The peripheral‐isolated populations in Sweden seem to have suffered from one or more severe bottlenecks, resulting in substantial genetic impoverishment. The peripheral‐connected eastern Baltic populations, on the other hand, are affected by post‐glacial and possibly recurrent gene flow from more central parts of the distribution.     

Contrasting patterns of mitochondrial and microsatellite genetic structure among Western European populations of tawny owls (Strix aluco)

A recent study of mitochondrial phylogeography of tawny owls (Strix aluco) in western Europe suggested that this species survived the Pleistocene glaciations in three allopatric refugia located in Iberia, Italy, and the Balkans, and the latter was likely the predominant source of postglacial colonization of northern Europe. New data from seven microsatellite loci from 184 individual owls distributed among 14 populations were used to assess the genetic congruence between nuclear and mitochondrial DNA (mtDNA) markers. Microsatellites corroborated the major phylogeographical conclusions reached on the basis of the mtDNA sequences, but also showed important differences leading to novel inferences. Microsatellites corroborated the three major refugia and supported the Balkan origin of northern populations. When corrected for differences in effective population size, microsatellites and mtDNA yielded generally congruent overall estimates of population structure (N*ST=0.12 vs. RST=0.16); however, there was substantial heterogeneity in the RST among the seven nuclear loci that was not correlated with heterozygosity. Populations representing the Balkans postglacial expansion interact with populations from the other two refugia forming two clines near the Alps and the Pyrenees. In both cases, the apparent position of the contact zones differed substantially between markers due to the genetic composition of populations sampled in northern Italy and Madrid. Microsatellite data did not corroborate the lower genetic diversity of northern, recently populated regions as was found with mtDNA; this discrepancy was taken as evidence for a recent bottleneck recovery. Finally, this study suggests that congruence among genetic markers should be more likely in cases of range expansion into new areas than when populations interact across contact zones.     

Isolation by distance and gene flow in the Eurasian badger (Meles meles) at both a local and broad scale

Eurasian badgers, Meles meles, have been shown to possess limited genetic population structure within Europe; however, field studies have detected high levels of philopatry, which are expected to increase population structure. Population structure will be a consequence of both contemporary dispersal and historical processes, each of which is expected to be evident at a different scale. Therefore, to gain a greater understanding of gene flow in the badger, we examined microsatellite diversity both among and within badger populations, focusing on populations from the British Isles and western Europe. We found that while populations differed in their allelic diversity, the British Isles displayed a similar degree of diversity to the rest of western Europe. The lower genetic diversity occurring in Ireland, Norway and Scotland was more likely to have resulted from founder effects rather than contemporary population density. While there was significant population structure (F ST = 0.19), divergence among populations was generally well explained by geographic distance (P < 0.0001) across the entire range studied of more than 3000 km. Transient effects from the Pleistocene appear to have been replaced by a strong pattern of genetic isolation by distance across western Europe, suggestive of colonization from a single refugium. Analysis of individuals within British populations through Mantel tests and spatial autocorrelation demonstrated that there was significant local population structure across 3-30 km, confirming that dispersal is indeed restricted. The isolation by distance observed among badger populations across western Europe is likely to be a consequence of this restricted local dispersal.     

Biogeographical connections between the Maghreb and the Mediterranean peninsulas of southern Europe

The glacial–interglacial cycles have caused severe range modifications of species' distributions. In Europe, thermophilic species had to retreat into geographically distinct southern refugia during glaciations. This process produced strong genetic imprints, which are still detectable by the present pattern of genetic differentiation and the distribution of regional diversity. To reveal the biogeographical imprints in the western Mediterranean, we analysed 26 populations of the butterfly Maniola jurtina spread over large areas of its European and North African distribution range. The samples were analysed using allozyme electrophoresis. We detected three genetic groups, divided into Western Europe, Central/Eastern Europe, and Italy with the Maghreb. The North African samples randomly cluster within the Italian samples. Even the population sampled in Morocco is genetically closely related to these samples and not to the geographically neighbouring Iberian ones. Parameters of genetic diversity showed similar values over the whole study area. The observed genetic pattern reflects possible glacial refugia in Europe located in the Iberian Peninsula and the Balkans. For North Africa and Italy, our data reveal a colonization of Africa originating from Italy.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 693–703.     

Haplotype variation in a mitochondrial tandem repeat of Norway spruce (Picea abies) populations suggests a serious founder effect during postglacial re-colonization of the western Alps

Populations from 13 elevational transects of Norway spruce [Picea abies (L.) Karst] across the Alpine range were sampled to elucidate the geographical pattern of genetic variation in relation to postglacial re-colonization and to study elevational effects on haplotypic diversity. We assessed fragment length variation in a tandem repeat region of the mitochondrial (mt) nad1 intron 2. This maternally inherited genetic marker is suited to infer migration as it is dispersed by seed only. A total of 10 haplotypes was found, most of which were due to repeat copy number variation. An analysis of molecular variance (amova) showed that overall population differentiation was high (F(ST)=0.41), and it revealed a significant differentiation between monomorphic western and moderately to highly variable eastern Alpine populations. This phylogeographic pattern may be explained by a founder effect during postglacial re-colonization. An early arriving haplotype, assumed to originate from a western Carpathian refugium, could expand into suitable habitats, reducing the chances for establishment of subsequently arriving haplotypes. On the other hand, the high variation in populations within an Italian transect of the south-eastern Alps may be the consequence of merging migration pathways from and close distance to putative glacial refugia, most likely those assumed in the Carpathian mountains and on the Balkan peninsula or possibly in the central plains of Italy. An effect of elevation on haplotypic diversity was not evident, though a low, but significant, partition of total genetic variation was attributed to among-population variation in one Italian transect. Various factors, such as vertical seed dispersal and forest management, may account for blurring an otherwise established pattern of genetic variation on a small geographical scale.