Merging methods in molecular and ecological genetics to study the adaptation of plants to anthropogenic metal-polluted sites: implications for phytoremediation

Metallophyte species that occur naturally on metal-enriched soils represent major biological resources for the improvement of phytoremediation, a benign and cost-effective technology that uses plants to clean up anthropogenic metal-polluted soils. Within the last decade, molecular genetic studies carried out on several model organisms (including Arabidopsis halleri) have considerably enhanced our understanding of metal tolerance and hyperaccumulation in plants, but the identification of the genes of interest for phytoremediation purposes remains a challenge. To meet this challenge, we propose to combine '-omics' with molecular ecology methods. Using A. halleri, we confronted molecular genetic results with: (i) within-species polymorphism and large-scale population differentiation for zinc tolerance; (ii) the demographical context (e.g. migration pattern) of the species for zinc tolerance evolution; (iii) the Quantitative Trait Loci (QTL) analysis of the genetic architecture for zinc tolerance; and (iv) the fine-scale dissection of identified QTL regions, to discuss more precisely the nature of the genes potentially involved in the adaptation to zinc-polluted soils.     

Demographic history of the trace metal hyperaccumulator Noccaea caerulescens (J. Presl and C. Presl) F. K. Mey. in Western Europe

Noccaea caerulescens (Brassicaceae) is a major pseudometallophyte model for the investigation of the genetics and evolution of metal hyperaccumulation in plants. We studied the population genetics and demographic history of this species to advance the understanding of among‐population differences in metal hyperaccumulation and tolerance abilities. Sampling of seven to 30 plants was carried out in 62 sites in Western Europe. Genotyping was carried out using a combination of new chloroplast and nuclear neutral markers. A strong genetic structure was detected, allowing the definition of three genetic subunits. Subunits showed a good geographic coherence. Accordingly, distant metallicolous populations generally belonged to distinct subunits. Approximate Bayesian computation analysis of demographic scenarios among subunits further supported a primary isolation of populations from the southern Massif Central prior to last glacial maximum, whereas northern populations may have derived during postglacial recolonization events. Estimated divergence times among subunits were rather recent in comparison with the species history, but certainly before the establishment of anthropogenic metalliferous sites. Our results suggest that the large‐scale genetic structure of N. caerulescens populations pre‐existed to the local adaptation to metalliferous sites. The population structure of quantitative variation for metal‐related adaptive traits must have established independently in isolated gene pools. However, features of the most divergent genetic unit (e.g. extreme levels of Cd accumulation observed in previous studies) question the putative relationships between adaptive evolution of metal‐related traits and subunits isolation. Finally, admixture signals among distant metallicolous populations suggest a putative role of human activities in facilitating long‐distance genetic exchanges.     

Phylogeography of the high alpine plant Senecio halleri (Asteraceae) in the European Alps: in situ glacial survival with postglacial stepwise dispersal into peripheral areas

Whether alpine plant species survived Pleistocene glaciations in situ on high alpine nunatak mountains is still under debate. To test this hypothesis, Senecio halleri, a high alpine and endemic species with a narrow distribution range in the European Alps, was chosen as a model organism. Polymerase chain reaction-restriction fragment length polymorphisms of chloroplast DNA (cpDNA PCR-RFLPs) were used in a phylogeographic analysis of 14 populations of S. halleri, covering its total distribution area. The results of haplotype diversity and distribution gave evidence of in situ glacial survival on siliceous central-alpine nunatak mountains in two areas, southwest and northeast of the Aosta valley. According to the absence of genetic differentiation between these two nunatak areas (based on amova), nested clade analysis implied a history of preglacial gene flow, in situ survival and extinction of intermediate populations during glaciation and postglacial stepwise recolonization of peripheral and intermediate areas.     

The population genomic basis of geographic differentiation in North American common ragweed (Ambrosia artemisiifolia L.)

Common ragweed (Ambrosia artemisiifolia L.) is an invasive, wind‐pollinated plant nearly ubiquitous in disturbed sites in its eastern North American native range and present across growing portions of Europe, Africa, Asia, and Australia. Phenotypic divergence between European and native‐range populations has been described as rapid evolution. However, a recent study demonstrated major human‐mediated shifts in ragweed genetic structure before introduction to Europe and suggested that native‐range genetic structure and local adaptation might fully explain accelerated growth and other invasive characteristics of introduced populations. Genomic differentiation that potentially influenced this structure has not yet been investigated, and it remains unclear whether substantial admixture during historical disturbance of the native range contributed to the development of invasiveness in introduced European ragweed populations. To investigate fine‐scale population genetic structure across the species' native range, we characterized diallelic SNP loci via a reduced‐representation genotyping‐by‐sequencing (GBS) approach. We corroborate phylogeographic domains previously discovered using traditional sequencing methods, while demonstrating increased power to resolve weak genetic structure in this highly admixed plant species. By identifying exome polymorphisms underlying genetic differentiation, we suggest that geographic differentiation of this important invasive species has occurred more often within pathways that regulate growth and response to defense and stress, which may be associated with survival in North America's diverse climatic regions.     

Smells like home: Desert ants, Cataglyphis fortis, use olfactory landmarks to pinpoint the nest

Background

Although some mechanisms of habitat adaptation of conspecific populations have been recently elucidated, the evolution of female preference has rarely been addressed as a force driving habitat adaptation in natural settings. Habitat adaptation of fire salamanders (Salamandra salamandra), as found in Middle Europe (Germany), can be framed in an explicit phylogeographic framework that allows for the evolution of habitat adaptation between distinct populations to be traced. Typically, females of S. salamandra only deposit their larvae in small permanent streams. However, some populations of the western post-glacial recolonization lineage use small temporary ponds as larval habitats. Pond larvae display several habitat-specific adaptations that are absent in stream-adapted larvae. We conducted mate preference tests with females from three distinct German populations in order to determine the influence of habitat adaptation versus neutral genetic distance on female mate choice. Two populations that we tested belong to the western post-glacial recolonization group, but are adapted to either stream or pond habitats. The third population is adapted to streams but represents the eastern recolonization lineage.

Results

Despite large genetic distances with F_ST values around 0.5, the stream-adapted females preferred males from the same habitat type regardless of genetic distance. Conversely, pond-adapted females did not prefer males from their own population when compared to stream-adapted individuals of either lineage.

Conclusion

A comparative analysis of our data showed that habitat adaptation rather than neutral genetic distance correlates with female preference in these salamanders, and that habitat-dependent female preference of a specific pond-reproducing population may have been lost during adaptation to the novel environmental conditions of ponds.     

Range-wide phylogeography of the European temperate-montane herbaceous plant Meum athamanticum Jacq.: evidence for periglacial persistence

Aim  The aim of this study is to analyse the genetic population structure of Meum athamanticum Jacq. in order to explore the alternative hypotheses (1) that the central and northern highland populations are the result of post-glacial recolonization from southern refugia, and the disjunct distribution of M. athamanticum can be explained by modern ecological conditions, or (2) that extant populations north of the Alps and Pyrenees persisted in situ during glacial periods.
Location  Europe.
Methods  Variation of amplified fragment length polymorphisms (AFLPs) was analysed for 23 populations from the entire range of the species. We used band-based approaches and methods based on allele frequencies to measure genetic diversity and to identify population structure.
Results  Our analyses reveal a north–south differentiation within M. athamanticum . High levels of genetic diversity, as well as private fragments, are found in populations both north and south of the Alps. Differentiation among populations is lower in the northern than in the southern population group, and significant isolation-by-distance is found only in the latter group.
Main conclusions  Our results indicate that M. athamanticum survived the last ice age in multiple refugia throughout its contemporary range and did not expand into areas north of the Alps from southern refugia. We found evidence that regional-scale migration in northern, formerly periglacial, parts of the species range has resulted in the intermingling of populations. In contrast, southern populations are characterized by long-term isolation. The south-west Alps represent an area where immigration and mixing of populations from northern and southern refugia appears to have taken place.     

Assessing natural and disturbed population structure in European grayling Thymallus thymallus: melding phylogeographic,population genetic and jurisdictional perspectives for conservation planning

Natural and human‐mediated population structure of European grayling Thymallus thymallus was assessed in primarily Austrian reaches of the Danube River catchment. Data on phylogeographic structure based on mitochondrial DNA (mtDNA) were combined with variation found across 13 microsatellite loci to assess introgression stemming from stocking activities. Populations north of the Alps generally showed no signs of long‐term introgression from allochthonous stocks, although one population comprised two distinct genotypic groups, one of which may stem from recently stocked material. South of the Alps, levels of introgression with stocks from the north were extensive and only one of six populations is believed to represent a reference state. Allelic diversity and expected heterozygosity were positively correlated with mtDNA admixture supporting more recent introgression and that there is little or no reproductive barrier between these two major lineages north and south of the Alps. A third unrelated mtDNA lineage is described from the Lafnitz, a tributary of the Raab drainage. The high lineage diversity in the upper Austrian Danube is not concordant with an existing model of T. thymallus evolutionarily significant units in Europe. Caveats in naming such units or following a strict hierarchical conservation unit structure for broadly distributed species with complex phylogeographic distributions stretching over various jurisdictions are discussed. The necessity of using both phylogeographic and population genetic approaches in evaluating the history and conservation value of populations in a conservation context is additionally highlighted.     

The role of geography and ecology in shaping repeated patterns of morphological and genetic differentiation between European minnows (Phoxinus phoxinus) from the Pyrenees and the Alps

Neutral and selective processes can drive repeated patterns of evolution in different groups of populations experiencing similar ecological gradients. In this paper, we used a combination of nuclear and mitochondrial DNA markers, as well as geometric morphometrics, to investigate repeated patterns of morphological and genetic divergence of European minnows in two mountain ranges: the Pyrenees and the Alps. European minnows (Phoxinus phoxinus) are cyprinid fish inhabiting most freshwater bodies in Europe, including those in different mountain ranges that could act as major geographical barriers to gene flow. We explored patterns of P. phoxinus phenotypic and genetic diversification along a gradient of altitude common to the two mountain ranges, and tested for isolation by distance (IBD), isolation by environment (IBE) and isolation by adaptation (IBA). The results indicated that populations from the Pyrenees and the Alps belong to two well differentiated, reciprocally monophyletic mtDNA lineages. Substantial genetic differentiation due to geographical isolation within and between populations from the Pyrenees and the Alps was also found using rapidly evolving AFLPs markers (isolation by distance or IBD), as well as morphological differences between mountain ranges. Also, morphology varied strongly with elevation and so did genetic differentiation to a lower extent. Despite moderate evidence for IBE and IBA, and therefore of repeated evolution, substantial population heterogeneity was found at the genetic level, suggesting that selection and population specific genetic drift act in concert to affect genetic divergence.     

It's about time: divergence, demography, and the evolution of developmental modes in marine invertebrates

Differences in larval developmental mode are predicted to affect ecological and evolutionary processes ranging from gene flow and population bottlenecks to rates of population recovery from anthropogenic disturbance and capacity for local adaptation. The most powerful tests of these predictions use comparisons among species to ask how phylogeographic patterns are correlated with the evolution and loss of prolonged planktonic larval development. An important and largely untested assumption of these studies is that interspecific differences in population genetic structure are mainly caused by differences in dispersal and gene flow (rather than by differences in divergence times among populations or changes in effective population sizes), and that species with similar patterns of spatial genetic variation have similar underlying temporal demographic histories. Teasing apart these temporal and spatial patterns is important for understanding the causes and consequences of evolutionary changes in larval developmental mode. New analytical methods that use the coalescent history of allelic diversity can reveal these temporal patterns, test the strength of traditional population-genetic explanations for variation in spatial structure based on differences in dispersal, and identify strongly supported alternative explanations for spatial structure based on demographic history rather than on gene flow alone. We briefly review some of these recent analytical developments, and show their potential for refining ideas about the correspondence between the evolution of larval developmental mode, population demographic history, and spatial genetic variation.     

Genetic Variation of Sesleria albicans Kit. ex Schultes (Poaceae): Lack of Evidence for Glacial Relict Endemism in Central Europe

Abstract: The populations of Sesleria albicans Kit. ex Schultes in central Europe are supposed to be glacial relicts. The genetic structure of these populations can provide evidence for the reliability of this hypothesis, since a distinct geographical clustering of populations and high levels of interpopulational genetic variation can be expected in the case of relict endemism. In the study presented here, we used Random Amplified Polymorphic DNA (RAPD) analysis to describe the genetic structure of 25 Sesleria albicans populations from west and central Germany, southwest Germany and the Alps. In the RAPD analysis 344 fragments could be amplified, of which 95.9 % were polymorphic. The percentage of polymorphic bands per population ranged from 29.7 % to 56.7 % and correlated significantly with population size, indicating a higher level of inbreeding in small and isolated populations. An analysis of molecular variance (AMOVA) revealed that 61.22 % of the variation resided within populations, whereas 34.25 % was found among populations within regions and only 4.53 % among regions. Genetic distance among populations (φ_ST) varied between 0.63 and 0.13, and in a Neighbour-Joining dendrogram based on the genetic distances between the investigated individuals, all populations could be discriminated from each other. The populations from the northern and southern Alps were clearly separated from the central European populations. These, however, did not form geographic clusters. Considering these results, Sesleria albicans showed a high level of intra- but only a low level of interpopulational genetic variation and very weak regional differentiation. The genetic pattern detected in this study, therefore, gives no evidence for glacial relict endemism of Sesleria albicans in central Europe.     

The population genetic structure of a large temperate pollinator species, Bombus pascuorum (Scopoli) (Hymenoptera: Apidae)

The genetic population structure of the bumble bee Bombus pascuorum was studied using six microsatellite loci and a partial sequence of the mitochondrial gene cytochrome b . Eighteen populations from central and northern Europe were included in the analysis. Observed levels of genetic variability and heterozygosity were high. Estimates of population differentiation based on F - and Φ-statistics revealed significant genetic differentiation among B. pascuorum populations and suggest that two partially isolated gene pools, separated by the Alps, do exist. The distribution of mtDNA haplotypes supports this view and presents direct evidence for gene flow across the Alps. Estimates of the number of migrants exchanged among populations north of the Alps suggest that historical events may have left a strong imprint on population structure.     

Glacial History Affected Phenotypic Differentiation in the Alpine Plant,Campanula thyrsoides

Numerous widespread Alpine plant species show molecular differentiation among populations from distinct regions. This has been explained as the result of genetic drift during glacial survival in isolated refugia along the border of the European Alps. Since genetic drift may affect molecular markers and phenotypic traits alike, we asked whether phenotypic differentiation mirrors molecular patterns among Alpine plant populations from different regions. Phenotypic traits can be under selection, so we additionally investigated whether part of the phenotypic differentiation can be explained by past selection and/or current adaptation. Using the monocarpic Campanula thyrsoides as our study species, a common garden experiment with plants from 21 populations from four phylogeographic groups located in regions across the Alps and the Jura Mountains was performed to test for differentiation in morphological and phenological traits. Past selection was investigated by comparing phenotypic differentiation among and within regions with molecular differentiation among and within regions. The common garden results indicated regional differentiation among populations for all investigated phenotypic traits, particularly in phenology. Delayed flowering in plants from the South-eastern Alps suggested adaptation to long sub-mediterranean summers and contrasted with earlier flowering of plants experiencing shorter growing seasons in regions with higher elevation to the West. Comparisons between molecular and phenotypic differentiation revealed diversifying selection among regions in height and biomass, which is consistent with adaptation to environmental conditions in glacial refugia. Within regions, past selection acted against strong diversification for most phenotypic traits, causing restricted postglacial adaptation. Evidence consistent with post-glacial adaptation was also given by negative correlation coefficients between several phenotypic traits and elevation of the population''s origin. In conclusion, our study suggests that, irrespective of adaptation of plants to their current environment, glacial history can have a strong and long-lasting influence on the phenotypic evolution of Alpine plants.     

Genetic differentiation among populations of Cicerbita alpina (L.) Wallroth (asteraceae) in the western Alps

In this study we analyzed the genetic population structure of the hygrophilous tall-herb Cicerbita alpina in the western Alps because this group of mountain plants is underrepresented in the biogeographical literature. AFLP (amplified fragment length polymorphism) fingerprints of 40 samples were analyzed from four populations situated in a transect from the southwestern Alps to the eastern part of the western Alps and one population from the Black Forest outside the Alps. Two genetic groups can be distinguished. The first group (A) comprises the populations from the northern and eastern parts of the western Alps, and the second group (B) comprises the populations from the southwestern Alps and the Black Forest. Group A originates most likely from at least one refugium in the southern piedmont regions of the Alps. This result provides molecular evidence for a humid climate at the southern margin of the Alps during the Würm glaciation. Group B originates presumably from western or northern direction and we discuss two possible scenarios for the colonization of the Alps, i.e. (1) long-distance dispersal from southwestern refugia and (2) colonization from nearby refugia in the western and/or northern Alpine forelands. The study demonstrates that the target species harbours considerable genetic diversity, even on a regional scale, and therefore is a suitable model for phylogeographic research.     

Diversification in a biodiversity hot spot: landscape correlates of phylogeographic patterns in the African spotted reed frog

The Eastern Afromontane Biodiversity Hotspot is known for microendemism and exceptional population genetic structure. The region's landscape heterogeneity is thought to limit gene flow between fragmented populations and create opportunities for regional adaptation, but the processes involved are poorly understood. Using a combination of phylogeographic analyses and circuit theory, I investigate how characteristics of landscape heterogeneity including regional distributions of slope, rivers and streams, habitat and hydrological basins (drainages) impact genetic distance among populations of the endemic spotted reed frog (Hyperolius substriatus), identifying corridors of connectivity as well as barriers to dispersal. Results show that genetic distance among populations is most strongly correlated to regional and local hydrologic structure and the distribution of suitable habitat corridors, not isolation by distance. Contrary to expectations, phylogeographic structure is not coincident with the two montane systems, but instead corresponds to the split between the region's two major hydrological basins (Zambezi and East Central Coastal). This results in a paraphyletic relationship for the Malawian Highlands populations with respect to the Eastern Arc Mountains and implies that the northern Malawian Highlands are the diversity centre for H. substriatus. Although the Malawian Highlands collectively hold the greatest genetic diversity, individual populations have lower diversity than their Eastern Arc counterparts, with an overall pattern of decreasing population diversity from north to south. Through the study of intraspecific differentiation across a mosaic of ecosystem and geographic heterogeneity, we gain insight into the processes of diversification and a broader understanding of the role of landscape in evolution.     

Lasting through the ice age: The role of the proglacial refugia in the maintenance of genetic diversity,population growth,and high dispersal rate in a widespread freshwater crustacean

1. The severe climatic changes during the Pleistocene ice ages have shaped the genetic structure and distribution of biota in Europe. We aimed to reveal in detail the genetic diversity, geographical population structure, historical and present demography, migration patterns, and the presence of possible glacial refugia within the nominative subspecies Asellus aquaticus aquaticus.
2. We analysed DNA sequences of the mitochondrial cytochrome c oxidase subunit I gene and nuclear noncoding internal transcribed spacer II region, from populations inhabiting post-glacial Europe (from the British Isles and Scandinavia to the northern Mediterranean and Black Sea coasts).
3. The origin of the taxon, including establishment in the Dinaric Western Balkans, dates to the Middle/Late Pliocene, but most of its genetic diversity emerged during the Middle/Late Pleistocene before the Last Glacial Maximum.
4. Despite the general absence of spatial genetic structure with population growth, we discovered two different phylogeographic stories across 11 clusters revealed by a coalescent approach. Firstly, the periglacial cluster group—spatially restricted mainly to the northern Balkans, Pannonian Basin, and Pontic Region—is older and more divergent. It apparently retained a relatively stable population size during the glacial-interglacial cycles. Conversely, the proglacial cluster group—widely distributed in areas close to the glacier margins (north of the Alps, Sudetes, Carpathians) and in the Pannonian Basin—is younger and composed of closely related individuals. It originated in Pleistocene and lasted continuously through the Last Glacial Maximum in numerous high latitude refugia. This was probably due to the vast network of proglacial lakes and rivers, which played a crucial role in the maintenance of genetic diversity, population growth, and high dispersal rate.
5. The evolutionary history of A. a. aquaticus reveals unexpected patterns and is an important lesson when making predictions for other aquatic taxa. Our results suggest that we should stop perceiving the proglacial habitats as lifeless ice desert.

     

Mechanisms of population differentiation in seabirds

Despite recent advances in population genetic theory and empirical research, the extent of genetic differentiation among natural populations of animals remains difficult to predict. We reviewed studies of geographic variation in mitochondrial DNA in seabirds to test the importance of various factors in generating population genetic and phylogeographic structure. The extent of population genetic and phylogeographic structure varies extensively among species. Species fragmented by land or ice invariably exhibit population genetic structure and most also have phylogeographic structure. However, many populations (26 of 37) display genetic structure in the absence of land, suggesting that other barriers to gene flow exist. In these populations, the extent of genetic structure is best explained by nonbreeding distribution: almost all species with two or more population-specific nonbreeding areas (or seasons) have phylogeographic structure, and all species that are resident at or near breeding colonies year-round have population genetic structure. Geographic distance between colonies and foraging range appeared to have a weak influence on the extent of population genetic structure, but little evidence was found for an effect of colony dispersion or population bottlenecks. In two species (Galapagos petrel, Pterodroma phaeopygia, and Xantus's murrelet, Synthliboramphus hypoleucus), population genetic structure, and even phylogeographic structure, exist in the absence of any recognizable physical or nonphysical barrier, suggesting that other selective or behavioural processes such as philopatry may limit gene flow. Retained ancestral variation may be masking barriers to dispersal in some species, especially at high latitudes. Allopatric speciation undoubtedly occurs in this group, but reproductive isolation also appears to have evolved through founder-induced speciation, and there is strong evidence that parapatric and sympatric speciation occur. While many questions remain unanswered, results of the present review should aid conservation efforts by enabling managers to predict the extent of population differentiation in species that have not yet been studied using molecular markers, and, thus, enable the identification of management units and evolutionary significant units for conservation.     

Molecular analysis of the Pleistocene history of Saxifraga oppositifolia in the Alps

A recent circumpolar survey of chloroplast DNA (cpDNA) haplotypes identified Pleistocene glacial refugia for the Arctic-Alpine Saxifraga oppositifolia in the Arctic and, potentially, at more southern latitudes. However, evidence for glacial refugia within the ice sheet covering northern Europe during the last glacial period was not detected either with cpDNA or in another study of S. oppositifolia that surveyed random amplified polymorphic DNA (RAPD) variation. If any genotypes survived in such refugia, they must have been swamped by massive postglacial immigration of periglacial genotypes. The present study tested whether it is possible to reconstruct the Pleistocene history of S. oppositifolia in the European Alps using molecular methods. Restriction fragment length polymorphism (RFLP) analysis of cpDNA of S. oppositifolia, partly sampled from potential nunatak areas, detected two common European haplotypes throughout the Alps, while three populations harboured two additional, rare haplotypes. RAPD analysis confirmed the results of former studies on S. oppositifolia; high within, but low among population genetic variation and no particular geographical patterning. Some Alpine populations were not perfectly nested in this common gene pool and contained private RAPD markers, high molecular variance or rare cpDNA haplotypes, indicating that the species could possibly have survived on ice-free mountain tops (nunataks) in some parts of the Alps during the last glaciation. However, the overall lack of a geographical genetic pattern suggests that there was massive immigration of cpDNA and RAPD genotypes by seed and pollen flow during postglacial times. Thus, the glacial history of S. oppositifolia in the Alps appears to resemble closely that suggested previously for the species in northern Europe.     

Mitochondrial DNA variation in Pleistocene and modern Atlantic salmon from the Iberian glacial refugium

Current understanding of the postglacial colonization of Nearctic and Palearctic species relies heavily on inferences drawn from the phylogeographic analysis of contemporary generic variants. Modern postglacial populations are supposed to be representative of their Pleistocene ancestors, and their current distribution is assumed to reflect the different colonization success and dispersal patterns of refugial lineages. Yet, testing of phylogeographic models against ancestral genomes from glacial refugia has rarely been possible. Here we compare ND1 mitochondrial DNA variation in late Pleistocene (16,000-40,000 years before present), historical and contemporary Atlantic salmon (Salmo salar) populations from northern Spain and other regions of western Europe. Our study demonstrates the presence of Atlantic salmon in the Iberian glacial refugium during the last 40,000 years and points to the Iberian Peninsula as the likely source of the most common haplotype within the Atlantic lineage in Europe. However, our findings also suggest that there may have been significant changes in the genetic structure of the Iberian refugial stock since the last ice age, and question whether modern populations in refugial areas are representative of ice age populations. A common haplotype that persisted in the Iberian Peninsula during the Pleistocene last glacial maximum is now extremely rare or absent from European rivers, highlighting the need for caution when making phylogeographic inferences about the origin and distribution of modern genetic types.     

From connectivity to isolation: genetic consequences of population fragmentation in capercaillie across Europe

The capercaillie inhabits a continuous range in large parts of the Palearctic boreal forest, but is patchily distributed in temperate Europe. An ongoing population decline, largely related to human land use changes, has been most pronounced in central and western Europe, where some local populations have become extinct. In this study, we document the genetic differentiation of capercaillie populations at different stages along a gradient of spatial structuring from high connectivity (continuous range in the boreal forest) to a metapopulation systems (Alps) and recent (central Europe) and historic (Pyrenees) isolation. Four hundred and sixty individuals from 14 sample sites were genotyped at 10 polymorphic microsatellite loci to assess genetic structure and variation of capercaillie populations across its European range. As expected, differentiation was least pronounced within the continuous range in the boreal forest. Within the metapopulation system of the Alps, differentiation was less than among the isolated populations of central Europe (Black Forest, Fichtelgebirge, Thuringia, Vosges). In the long-isolated population of the Pyrenees, and the recently isolated populations of central Europe, genetic diversity was significantly reduced compared with the Alps and boreal forest. Our results agree with the concept of a gradual increase in genetic differentiation from connectivity to isolation, and from recent to historic isolation. Anthropogenic habitat deterioration and fragmentation thus not only leads to range contractions and extinctions, but may also have significant genetic and evolutionary consequences for surviving populations. To maintain high levels of genetic variation in species in fragmented habitats, conservation should aim at securing connectivity between spatially distinct populations.     

Post-glacial history of the dominant alpine sedge Carex curvula in the European Alpine System inferred from nuclear and chloroplast markers

The alpine sedge Carex curvula ssp. curvula is a clonal, dominant graminoid found in the European Alps, the Carpathians, the Pyrenees and in some of the Balkan Mountains. It is a late-successional species of acidophilous alpine meadows that occurs on sites that were covered by ice during the last glacial maximum (LGM). By applying the amplified fragment length polymorphism (AFLP) fingerprinting and chloroplast DNA (cpDNA) sequencing, we attempted to identify the recolonization routes followed by the species after the last ice retreat. We relied on the genetic diversity of 37 populations covering the entire distributional range of the species. As a wind-pollinated species, C. curvula is characterized by a low level of population genetic differentiation. Nuclear and chloroplast data both support the hypothesis of a long-term separation of Eastern (Balkans and Carpathians) and Western (Alps and Pyrenees) lineages. In the Alps, a continuum of genetic depauperation from the east to the west may be related to a recolonization wave originating in the eastern-most parts of the chain, where the main glacial refugium was likely located. The Pyrenean populations are nested within the western Alps group and show a low level of genetic diversity, probably due to recent long-distance colonization. In contrast to the Alps, we found no phylogeographical structure in the Carpathians. The combination of reduced ice extension during the Würm period and the presence of large areas of siliceous substrate at suitable elevation suggest that in contrast to populations in the Alps, the species in the Carpathians underwent a local vertical migration rather than extinction and recolonization over long distance.