Land masses and oceanic currents drive population structure of Heritiera littoralis,a widespread mangrove in the Indo‐West Pacific

Phylogeographic forces driving evolution of sea‐dispersed plants are often influenced by regional and species characteristics, although not yet deciphered at a large spatial scale for many taxa like the mangrove species Heritiera littoralis. This study aimed to assess geographic distribution of genetic variation of this widespread mangrove in the Indo‐West Pacific region and identify the phylogeographic factors influencing its present‐day distribution. Analysis of five chloroplast DNA fragments’ sequences from 37 populations revealed low genetic diversity at the population level and strong genetic structure of H. littoralis in this region. The estimated divergence times between the major genetic lineages indicated that glacial level changes during the Pleistocene epoch induced strong genetic differentiation across the Indian and Pacific Oceans. In comparison to the strong genetic break imposed by the Sunda Shelf toward splitting the lineages of the Indian and Pacific Oceans, the genetic differentiation between Indo‐Malesia and Australasia was not so prominent. Long‐distance dispersal ability of H. littoralis propagules helped the species to attain transoceanic distribution not only across South East Asia and Australia, but also across the Indian Ocean to East Africa. However, oceanic circulation pattern in the South China Sea was found to act as a barrier creating further intraoceanic genetic differentiation. Overall, phylogeographic analysis in this study revealed that glacial vicariance had profound influence on population differentiation in H. littoralis and caused low genetic diversity except for the refugia populations near the equator which might have persisted through glacial maxima. With increasing loss of suitable habitats due to anthropogenic activities, these findings therefore emphasize the urgent need for conservation actions for all populations throughout the distribution range of H. littoralis.     

Holocene re‐colonisation,central–marginal distribution and habitat specialisation shape population genetic patterns within an Atlantic European grass species

Corynephorus canescens (L.) P.Beauv. is an outbreeding, short‐lived and wind‐dispersed grass species, highly specialised on scattered and disturbance‐dependent habitats of open sandy sites. Its distribution ranges from the Iberian Peninsula over Atlantic regions of Western and Central Europe, but excludes the two other classical European glacial refuge regions on the Apennine and Balkan Peninsulas. To investigate genetic patterns of this uncommon combination of ecological and biogeographic species characteristics, we analysed AFLP variation among 49 populations throughout the European distribution range, expecting (i) patterns of SW European glacial refugia and post‐glacial expansion to the NE; (ii) decreasing genetic diversity from central to marginal populations; and (iii) interacting effects of high gene flow and disturbance‐driven genetic drift. Decreasing genetic diversity from SW to NE and distinct gene pool clustering imply refugia on the Iberian Peninsula and in western France, from where range expansion originated towards the NE. High genetic diversity within and moderate genetic differentiation among populations, and a significant pattern of isolation‐by‐distance indicate a gene flow drift equilibrium within C. canescens, probably due to its restriction to scattered and dynamic habitats and limited dispersal distances. These features, as well as the re‐colonisation history, were found to affect genetic diversity gradients from central to marginal populations. Our study emphasises the need for including the specific ecology into analyses of species (re–)colonisation histories and range centre–margin analyses. To account for discontinuous distributions, new indices of marginality were tested for their suitability in studies of centre–periphery gradients.     

Spatial and temporal genetic dynamics of the grasshopper Oedaleus decorus revealed by museum genomics

Analyzing genetic variation through time and space is important to identify key evolutionary and ecological processes in populations. However, using contemporary genetic data to infer the dynamics of genetic diversity may be at risk of a bias, as inferences are performed from a set of extant populations, setting aside unavailable, rare, or now extinct lineages. Here, we took advantage of new developments in next‐generation sequencing to analyze the spatial and temporal genetic dynamics of the grasshopper Oedaleus decorus, a steppic Southwestern‐Palearctic species. We applied a recently developed hybridization capture (hyRAD) protocol that allows retrieving orthologous sequences even from degraded DNA characteristic of museum specimens. We identified single nucleotide polymorphisms in 68 historical and 51 modern samples in order to (i) unravel the spatial genetic structure across part of the species distribution and (ii) assess the loss of genetic diversity over the past century in Swiss populations. Our results revealed (i) the presence of three potential glacial refugia spread across the European continent and converging spatially in the Alpine area. In addition, and despite a limited population sample size, our results indicate (ii) a loss of allelic richness in contemporary Swiss populations compared to historical populations, whereas levels of expected heterozygosities were not significantly different. This observation is compatible with an increase in the bottleneck magnitude experienced by central European populations of O. decorus following human‐mediated land‐use change impacting steppic habitats. Our results confirm that application of hyRAD to museum samples produces valuable information to study genetic processes across time and space.     

Mitochondrial gene trees support persistence of cold tolerant fairy shrimp throughout the Pleistocene glaciations in both southern and more northerly refugia

Fairy shrimp (Crustacea: Anostraca) are specialist inhabitants of temporary aquatic habitats. In many parts of the world and particularly in Western Europe, however, populations are declining while the development of adequate conservation strategies is impeded by a poor knowledge of the genetic structure and taxonomic status of remaining lineages. We reconstructed a phylogeography of the species Chirocephalus diaphanus Prévost, 1803 using partial sequences of the mitochondrial COI gene and discuss the importance of different Pleistocene refugia to explain current diversity patterns. In addition to 20 C. diaphanus populations, we also included populations of six presumably closely related chirocephalids to evaluate their taxonomic status. Based on molecular data, the Eastern European subspecies C. diaphanus romanicus deserves species status while the species status of two Italian chirocephalids, C. salinus and C. ruffoi is questionable. Results indicate European C. diaphanus lineages diverged well before the last glacial maximum and survived the Pleistocene glaciations in multiple (sub)refugia along the Iberian, Italian, and Balkan peninsula. Northern Europe was subsequently recolonized from Southern France, resulting in high levels of cryptic diversity around glacial refugia but also in more widespread haplotypes in mainland Europe.     

Unravelling the evolutionary history and future prospects of endemic species restricted to former glacial refugia

The contemporary distribution and genetic composition of biodiversity bear a signature of species’ evolutionary histories and the effects of past climatic oscillations. For many European species, the Mediterranean peninsulas of Iberia, Italy and the Balkans acted as glacial refugia and the source of range recolonization, and as a result, they contain disproportionately high levels of diversity. As these areas are particularly threatened by future climate change, it is important to understand how past climatic changes affected their biodiversity. We use an integrated approach, combining markers with different evolutionary rates and combining phylogenetic analysis with approximate Bayesian computation and species distribution modelling across temporal scales. We relate phylogeographic processes to patterns of genetic variation in Myotis escalerai, a bat species endemic to the Iberian Peninsula. We found a distinct population structure at the mitochondrial level with a strong geographic signature, indicating lineage divergence into separate glacial refugia within the Iberian refugium. However, microsatellite markers suggest higher levels of gene flow resulting in more limited structure at recent time frames. The evolutionary history of M. escalerai was shaped by the effects of climatic oscillations and changes in forest cover and composition, while its future is threatened by climatically induced range contractions and the role of ecological barriers due to competition interactions in restricting its distribution. This study warns that Mediterranean peninsulas, which provided refuge for European biodiversity during past glaciation events, may become a trap for limited dispersal and ecologically limited endemic species under future climate change, resulting in loss of entire lineages.     

Insights into the neutral and adaptive processes shaping the spatial distribution of genomic variation in the economically important Moroccan locust (Dociostaurus maroccanus)

Understanding the processes that shape neutral and adaptive genomic variation is a fundamental step to determine the demographic and evolutionary dynamics of pest species. Here, we use genomic data obtained via restriction site‐associated DNA sequencing to investigate the genetic structure of Moroccan locust (Dociostaurus maroccanus) populations from the westernmost portion of the species distribution (Iberian Peninsula and Canary Islands), infer demographic trends, and determine the role of neutral versus selective processes in shaping spatial patterns of genomic variation in this pest species of great economic importance. Our analyses showed that Iberian populations are characterized by high gene flow, whereas the highly isolated Canarian populations have experienced strong genetic drift and loss of genetic diversity. Historical demographic reconstructions revealed that all populations have passed through a substantial genetic bottleneck around the last glacial maximum (~21 ka BP) followed by a sharp demographic expansion at the onset of the Holocene, indicating increased effective population sizes during warm periods as expected from the thermophilic nature of the species. Genome scans and environmental association analyses identified several loci putatively under selection, suggesting that local adaptation processes in certain populations might not be impeded by widespread gene flow. Finally, all analyses showed few differences between outbreak and nonoutbreak populations. Integrated pest management practices should consider high population connectivity and the potential importance of local adaptation processes on population persistence.     

Patterns of nuclear and mitochondrial DNA variation in Iberian populations of <Emphasis Type="Italic">Emys orbicularis</Emphasis> (Emydidae): conservation implications

The European pond turtle (Emys orbicularis) is threatened and in decline in several regions of its natural range, due to habitat loss combined with population fragmentation. In this work, we have focused our efforts on studying the genetic diversity and structure of Iberian populations with a fine-scale sampling (254 turtles in 10 populations) and a representation from North Africa and Balearic island populations. Using both nuclear and mitochondrial markers (seven microsatellites, ∼1048 bp nDNA and ∼1500 bp mtDNA) we have carried out phylogenetic and demographic analyses. Our results show low values of genetic diversity at the mitochondrial level although our microsatellite dataset revealed relatively high levels of genetic variability with a latitudinal genetic trend decreasing from southern to northern populations. A moderate degree of genetic differentiation was estimated for Iberian populations (genetic distances, F _ST values and clusters in the Bayesian analysis). The results in this study combining mtDNA and nDNA, provide the most comprehensive population genetic data for E. orbicularis in the Iberian Peninsula. Our results suggest that Iberian populations within the Iberian–Moroccan lineage should be considered as a single subspecies with five management units, and emphasize the importance of habitat management rather than population reinforcement (i.e. captive breeding and reintroduction) in this long-lived species.     

The integration of multiple independent data reveals an unusual response to Pleistocene climatic changes in the hard tick Ixodes ricinus

In the last few years, improved analytical tools and the integration of genetic data with multiple sources of information have shown that temperate species exhibited more complex responses to ice ages than previously thought. In this study, we investigated how Pleistocene climatic changes affected the current distribution and genetic diversity of European populations of the tick Ixodes ricinus, an ectoparasite with high ecological plasticity. We first used mitochondrial and nuclear genetic markers to investigate the phylogeographic structure of the species and its Pleistocene history using coalescent‐based methods; then we used species distribution modelling to infer the climatic niche of the species at last glacial maximum; finally, we reviewed the literature on the I. ricinus hosts to identify the locations of their glacial refugia. Our results support the scenario that during the last glacial phase, I. ricinus never experienced a prolonged allopatric divergence in separate glacial refugia, but persisted with interconnected populations across Southern and Central Europe. The generalist behaviour in host choice of I. ricinus would have played a major role in maintaining connections between its populations. Although most of the hosts persisted in separate refugia, from the point of view of I. ricinus, they represented a continuity of ‘bridges’ among populations. Our study highlights the importance of species‐specific ecology in affecting responses to Pleistocene glacial–interglacial cycles. Together with other cases in Europe and elsewhere, it contributes to setting new hypotheses on how species with wide ecological plasticity coped with Pleistocene climatic changes.     

The Pyrenees as a cradle of plant diversity: phylogeny,phylogeography and niche modeling of Saxifraga longifolia

The current distribution of most species results from ecological niche, past distribution, and migrations during glacial–interglacial periods and in situ evolution. Here, we disentangle the colonization history of Saxifraga longifolia Lapeyr., a limestone plant abundant in the Pyrenees and rare in other Iberian mountains and the African Atlas. Our working hypothesis is that the current distribution results from the shrinkage of a more extensive distribution in previous cold periods. We sampled 160 individuals of 32 populations across the whole distribution range and sequenced four DNA regions (rpl32-trnL, rps16-trnQ, trnS-trnG, and ITS). Ecological conditions were modeled to identify factors promoting high genetic diversity and long-term persistence areas for S. longifolia. In addition, we inferred phylogenetic relationships, phylogeographic divergence, genetic diversity, and migration routes. Seven plastid haplotypes were found, of which six occur in the Pyrenees and one in the High Atlas (Morocco). Discrete phylogeographic analysis (DPA) estimated migration routes predominantly from the Pyrenees to the other areas. Colonization events to those areas appear to have taken place recently given that the rest of the Iberian mountains do not harbor exclusive haplotypes. Iberian–Northern African distribution was inferred to be the result of long-distance dispersal because the split between Iberian and High Atlas haplotypes is estimated to have taken place in the last 4 million years ago when the Strait of Gibraltar was already open. Migrations from the Pyrenees to the south may have been favored by a corridor of predominant limestone rocks along Eastern Iberia, followed by successful overcoming the Strait of Gibraltar to reach northern Africa.     

Imprint of post-glacial history in a narrowly distributed endemic spruce, Picea alcoquiana, in central Japan observed in nuclear microsatellites and organelle DNA markers

Aim We aim to infer the post‐glacial history of the narrowly distributed endemic spruce Picea alcoquiana in Japan, and to assess the hypothesis that the existing narrow natural range of the species has resulted from the diminution of the past natural range since the last glacial period. Location Mountainous forests in central Honshu Island in Japan. Methods We assessed the geographical patterns of genetic variation across nine populations of P. alcoquiana across its natural range using five nuclear microsatellites and polymerase chain reaction–restriction fragment length polymorphism markers for chloroplast (cp) and mitochondrial (mt) DNA. This study focuses on the genetic differentiation between northern peripherally isolated and southern core populations within the natural range of the species in central Honshu. In addition, based on diagnostic morphological traits of the cone, we used reliable macrofossil evidence to gain further insight into the past natural range of the species. Results Picea alcoquiana shows a level of genetic differentiation among populations (Φ_ST = 0.082) that was higher than the levels observed in nuclear microsatellites for other anemophilous and widespread tree species in Japan. A notable finding for the nuclear microsatellites was the loss of rare alleles and strong evidence of a recent bottleneck in the peripherally isolated populations. Analysis of molecular variance in cpDNA and mtDNA markers showed an absence of genetic differentiation between the peripherally isolated and core populations. Macrofossil evidence indicated that the past natural range of the species extended to a lower elevation and c. 135 km north of the existing peripherally isolated populations during the last glacial period (c. 28,000 yr bp ). Main conclusions During the last glacial period, P. alcoquiana had a wider natural range in which the peripherally isolated and core populations could have been geographically continuous with each other, and effective gene flow by means of pollen and seeds might have occurred. The recent bottleneck and consequent loss of rare alleles in the peripherally isolated populations might have evolved during the diminution and retreat of the northern part of the past natural range southwards to the core area and during the subsequent separation of the peripherally isolated populations from the core area since the last glacial period.     

Climatic niche and neutral genetic diversity of the six Iberian pine species: a retrospective and prospective view

Quaternary climatic fluctuations have left contrasting historical footprints on the neutral genetic diversity patterns of existing populations of different tree species. We should expect the demography, and consequently the neutral genetic structure, of taxa less tolerant to particular climatic extremes to be more sensitive to long‐term climate fluctuations. We explore this hypothesis here by sampling all six pine species found in the Iberian Peninsula (2464 individuals, 105 populations), using a common set of chloroplast microsatellite markers, and by looking at the association between neutral genetic diversity and species‐specific climatic requirements. We found large variation in neutral genetic diversity and structure among Iberian pines, with cold‐enduring mountain species (Pinus uncinata, P. sylvestris and P. nigra) showing substantially greater diversity than thermophilous taxa (P. pinea and P. halepensis). Within species, we observed a significant positive correlation between population genetic diversity and summer precipitation for some of the mountain pines. The observed pattern is consistent with the hypotheses that: (i) more thermophilous species have been subjected to stronger demographic fluctuations in the past, as a consequence of their maladaptation to recurrent glacial cold stages; and (ii) altitudinal migrations have allowed the maintenance of large effective population sizes and genetic variation in cold‐tolerant species, especially in more humid regions. In the light of these results and hypotheses, we discuss some potential genetic consequences of impending climate change.     

Evidence for a large-scale population structure of Arabidopsis thaliana from genome-wide single nucleotide polymorphism markers

Population-based methods for the genetic mapping of adaptive traits and the analysis of natural selection require that the population structure and demographic history of a species are taken into account. We characterized geographic patterns of genetic variation in the model plant Arabidopsis thaliana by genotyping 115 genome-wide single nucleotide polymorphism (SNP) markers in 351 accessions from the whole species range using a matrix-assisted laser desorption/ionization time-of-flight assay, and by sequencing of nine unlinked short genomic regions in a subset of 64 accessions. The observed frequency distribution of SNPs is not consistent with a constant-size neutral model of sequence polymorphism due to an excess of rare polymorphisms. There is evidence for a significant population structure as indicated by differences in genetic diversity between geographic regions. Accessions from Central Asia have a low level of polymorphism and an increased level of genome-wide linkage disequilibrium (LD) relative to accessions from the Iberian Peninsula and Central Europe. Cluster analysis with the structure program grouped Eurasian accessions into K=6 clusters. Accessions from the Iberian Peninsula and from Central Asia constitute distinct populations, whereas Central and Eastern European accessions represent admixed populations in which genomes were reshuffled by historical recombination events. These patterns likely result from a rapid postglacial recolonization of Eurasia from glacial refugial populations. Our analyses suggest that mapping populations for association or LD mapping should be chosen from regional rather than a species-wide sample or identified genetically as sets of individuals with similar average genetic distances. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Strong genetic differentiation and low genetic diversity of the freshwater pearl mussel (<Emphasis Type="Italic">Margaritifera margaritifera</Emphasis> L.) in the southwestern European distribution range

Genetic diversity of European freshwater pearl mussel, Margaritifera margaritifera (L.), appears exceptional with highest genetic variability found in the northernmost European populations of Scandinavia and lower genetic variability in central and southern Europe. The objective of this study was to investigate genetic diversity and differentiation of 14 southernmost populations on the Iberian Peninsula which greatly differ in terms of life span and habitat conditions from the rest of central and northern European populations. The analyses of ten microsatellite loci revealed a pronounced level of genetic divergence and very low genetic diversity. These results match the expectations of geographically peripheral populations with respect to their genetic composition. The life history strategy, the narrow ecological niche of the species, and anthropogenic habitat modifications have most likely shaped the genetic pattern of Iberian pearl mussel populations. The peripheral position with less optimal habitat conditions may increase the extinction risk of these populations and thus effective conservation strategies for the Iberian M. margaritifera are needed. The successful conservation of the species at its southwestern margin requires inclusion of genetically different conservation units which may reveal local adaptation.     

Low genetic variability and strong differentiation among isolated populations of the rare steppe grass Stipa capillata L. in Central Europe

Stipa capillata L. (Poaceae) is a rare grassland species in Central Europe that is thought to have once been widespread in post‐glacial times. Such relict species are expected to show low genetic diversity within populations and high genetic differentiation between populations due to bottlenecks, long‐term isolation and ongoing habitat fragmentation. These patterns should be particularly pronounced in selfing species. We analysed patterns of random amplified polymorphic DNA (RAPD) variation in the facultatively cleistogamous S. capillata to examine whether genetic diversity is associated with population size, and to draw initial conclusions on the migration history of this species in Central Europe. We analysed 31 S. capillata populations distributed in northeastern, central and western Germany, Switzerland and Slovakia. Estimates of genetic diversity at the population level were low and not related to population size. Among all populations, extraordinarily high levels of genetic differentiation (amova : φ_ST = 0.86; Bayesian analysis: θ^B = 0.758) and isolation‐by‐distance were detected. Hierarchical amova indicated that most of the variability was partitioned among geographic regions (59%), or among populations between regions when the genetically distinct Slovakian populations were excluded. These findings are supported by results of a multivariate ordination analysis. We also found two different groups in an UPGMA cluster analysis: one that contained the populations from Slovakia, and the other that combined the populations from Germany and Switzerland. Our findings imply that S. capillata is indeed a relict species that experienced strong bottlenecks in Central Europe, enhanced by isolation and selfing. Most likely, populations in Slovakia were not the main genetic source for the post‐glacial colonization of Central Europe.     

The genetic structure of <Emphasis Type="Italic">Quercus crispula</Emphasis> in northeastern Japan as revealed by nuclear simple sequence repeat loci

Previous studies have reached different discussions about the genetic variation and genetic structure of Quercus crispula populations in northeastern Japan. This is a common oak species in Eastern Asia. Some studies have suggested that the populations in northeastern Japan were derived from those remaining in the southwest after the last glacial maximum (LGM), whilst other studies have found evidence that populations persisted in northeastern Japan during the LGM. Using seven highly polymorphic nuclear simple sequence repeat loci, we investigated the genetic structure of 16 Q. crispula populations along a latitudinal gradient in northeastern Japan (northern Honshu and Hokkaido), spanning about half of the species’ biogeographic range in the country. Although the level of population differentiation was low (F _ST = 0.021; G^￠_\textST G^{\prime}_{\text{ST}}  = 0.090), two geographically differentiated clusters were detected by STRUCTURE analysis. The first cluster included most of the populations in Hokkaido, and may indicate continued survival throughout past glacial periods. We found a significant decrease in allelic richness with latitude, so the second cluster may represent an expansion of the lineage from Honshu during the post-glacial period. These results should enhance our understanding of historical north–south migrations of this species in northeastern Japan.     

A complex scenario of glacial survival in Mediterranean and continental refugia of a temperate continental vole species (Microtus arvalis) in Europe

The role of glacial refugia in shaping contemporary species distribution is a long-standing question in phylogeography and evolutionary ecology. Recent studies are questioning previous paradigms on glacial refugia and postglacial recolonization pathways in Europe, and more flexible phylogeographic scenarios have been proposed. We used the widespread common vole Microtus arvalis as a model to investigate the origin, locations of glacial refugia, and dispersal pathways, in the group of “Continental” species in Europe. We used a Bayesian spatiotemporal diffusion analysis (relaxed random walk model) of cytochrome b sequences across the species range, including newly collected individuals from 10 Iberian localities and published sequences from 68 localities across 22 European countries. Our data suggest that the species originated in Central Europe, and we revealed the location of multiple refugia (in both southern peninsulas and continental regions) for this continental model species. Our results confirm the monophyly of Iberian voles and the pre-LGM divergence between Iberian and European voles. We found evidence of restricted postglacial dispersal from refugia in Mediterranean peninsulas. We inferred a complex evolutionary and demographic history of M. arvalis in Europe over the last 50,000 years that does not adequately fit previous glacial refugial scenarios. The phylogeography of M. arvalis provides a paradigm of ice-age survival of a temperate continental species in western and eastern Mediterranean peninsulas (sources of endemism) and multiple continental regions (sources of postglacial spread). Our findings also provide support for a major role of large European river systems in shaping geographic boundaries of M. arvalis in Europe.     

Signatures of demographic bottlenecks in European wolf populations

Monitoring the loss of genetic diversity in wild populations after a bottleneck event is a priority in conservation and management plans. Here, we used diverse molecular markers to search for signatures of demographic bottlenecks in two wolf populations; an isolated population from the Iberian Peninsula and a non-isolated population from European Russia. Autosomal, mtDNA and Y-chromosomal diversity and the effective population size (N_e) were significantly lower in the Iberian population. Neutrality tests using mtDNA sequences, such as R_2, Fu and Li’s F*, Tajima’s D and Fu’s F_s, were positively significant in the Iberian population, suggesting a population decline, but were not significant for the Russian population, likely due to its larger effective population size. However, three tests using autosomal data confirmed the occurrence of the genetic bottleneck in both populations. The M-ratio test was the only one providing significant results for both populations. Given the lack of consistency among the different tests, we recommend using multiple approaches to investigate possible past bottlenecks. The small effective population size (about 50) in the Iberian Peninsula compared to the presumed extant population size could indicate that the bottleneck was more powerful than initially suspected or an overestimation of the current population. The risks associated with small effective population sizes suggest that the genetic change in this population should be closely monitored in the future. On the other hand, the relatively small effective population size for Russian wolves (a few hundred individuals) could indicate some fragmentation, contrary to what is commonly assumed.     

Phylogeographic past and invasive presence of Arion pest slugs in Europe

Arion vulgaris (syn. A. lusitanicus) is the most destructive pest slug in Europe. The species has been regarded a classic case of an ongoing biological invasion with negative economic and ecological impact in many European countries, but this status has recently been contested. In this study, we assessed mitochondrial and autosomal genetic diversity in populations of A. vulgaris across the entire distribution range in order to characterize its evolutionary history. Mitochondrial diversity in A. vulgaris was strongly reduced compared with the closely related and largely codistributed noninvasive species A. rufus and A. ater, indicating a very rapid spread of A. vulgaris through Europe. Autosomal diversity assessed in 632 individuals from 32 populations decreased towards eastern and northern Europe which is consistent with the reported expansion of the species towards these regions in the last decades. Demographic simulations supported very recent population founding events in most of the European range. The short periods between the first detection of A. vulgaris in different countries and only a very weak association of genetic structuring among populations with geographical distances suggest a human contribution in the ongoing expansion of the slug. We propose that this contribution may ultimately prevent the exact localization of the debated region of origin of A. vulgaris. However, the reclassification of A. vulgaris as noninvasive would be premature. Without counter measures, the Eastern and Northern European countries can expect to see this biological invasion continued in the future.     

Phylogeography and genetic structure of the orchid Himantoglossum hircinum (L.) Spreng. across its European central–marginal gradient

Aim This study aims to link demographic traits and post‐glacial recolonization processes with genetic traits in Himantoglossum hircinum (L.) Spreng (Orchidaceae), and to test the implications of the central–marginal concept (CMC) in Europe. Location Twenty sites covering the entire European distribution range of this species. Methods We employed amplified fragment length polymorphism (AFLP) markers and performed a plastid microsatellite survey to assess genetic variation in 20 populations of H. hircinum located along central–marginal gradients. We measured demographic traits to assess population fitness along geographical gradients and to test for correlations between demographic traits and genetic diversity. We used genetic diversity indices and analyses of molecular variance (AMOVA) to test hypotheses of reduced genetic diversity and increased genetic differentiation and isolation from central to peripheral sites. We used Bayesian simulations to analyse genetic relationships among populations. Results Genetic diversity decreased significantly with increasing latitudinal and longitudinal distance from the distribution centre when excluding outlying populations. The AMOVA revealed significant genetic differentiation among populations (F_ST = 0.146) and an increase in genetic differentiation from the centre of the geographical range to the margins (except for the Atlantic group). Population fitness, expressed as the ratio N_R/N, decreased significantly with increasing latitudinal distance from the distribution centre. Flower production was lower in most eastern peripheral sites. The geographical distribution of microsatellite haplotypes suggests post‐glacial range expansion along three major migratory pathways, as also supported by individual membership fractions in six ancestral genetic clusters (C1–C6). No correlations between genetic diversity (e.g. diversity indices, haplotype frequency) and population demographic traits were detected. Main conclusions Reduced genetic diversity and haplotype frequency in H. hircinum at marginal sites reflect historical range expansions. Spatial variation in demographic traits could not explain genetic diversity patterns. For those sites that did not fit into the CMC, the genetic pattern is probably masked by other factors directly affecting either demography or population genetic structure. These include post‐glacial recolonization patterns and changes in habitat suitability due to climate change at the northern periphery. Our findings emphasize the importance of distinguishing historical effects from those caused by geographical variation in population demography of species when studying evolutionary and ecological processes at the range margins under global change.     

High genetic diversity declines towards the geographic range periphery of Adonis vernalis,a Eurasian dry grassland plant

Genetic diversity is important for species' fitness and evolutionary processes but our knowledge on how it varies across a species' distribution range is limited. The abundant centre hypothesis (ACH) predicts that populations become smaller and more isolated towards the geographic range periphery – a pattern that in turn should be associated with decreasing genetic diversity and increasing genetic differentiation. We tested this hypothesis in Adonis vernalis, a dry grassland plant with an extensive Eurasian distribution. Its life‐history traits and distribution characteristics suggest a low genetic diversity that decreases and a high genetic differentiation that increases towards the range edge. We analysed AFLP fingerprints in 28 populations along a 4698‐km transect from the geographic range core in Russia to the western range periphery in Central and Western Europe. Contrary to our expectation, our analysis revealed high genetic diversity (range of proportion of polymorphic bands = 56–81%, He = 0.168–0.238) and low genetic differentiation across populations (Φ_ST = 0.18). However, in congruence with the genetic predictions of the ACH, genetic diversity decreased and genetic differentiation increased towards the range periphery. Spanish populations were genetically distinct, suggesting a divergent post‐glacial history in this region. The high genetic diversity and low genetic differentiation in the remaining A. vernalis populations is surprising given the species' life‐history traits and points to the possibility that the species has been widely distributed in the studied region or that it has migrated from a diverse source in an East–West direction, in the past.