No evidence for nuclear introgression despite complete mtDNA replacement in the Carpathian newt (Lissotriton montandoni)

Patterns of interspecific introgression may vary geographically, and the distribution of introgressed variants can yield insight into the historical dynamics of genetic interactions between hybridizing species. Urodele amphibians, often characterized by limited mobility, deep intraspecific genetic structuring and vulnerability to climatic changes, constitute suitable models for such historical inferences. Here, we combine an extensive survey of the mitochondrial (mtDNA) and nuclear (15 microsatellites) genomes in the Carpathian newt, Lissotriton montandoni (Lm) with species distribution modelling (SDM). Populations of the smooth newt, L. vulgaris (Lv) from the areas surrounding the Lm range were also sampled to test whether gene flow between these hybridizing species extends beyond the area of strict syntopy. The extent of introgression differs dramatically between the mitochondrial genome and the nuclear genome. While multiple, spatially and temporally distinct introgression events from Lv resulted in complete mtDNA replacement in Lm, there was little evidence of recent interspecific nuclear gene flow in the assayed markers. Microsatellite differentiation within Lm defines three units, probably derived from separate glacial refugia, located in the northern, eastern and southern part of the Carpathians. In situ survival and range fragmentation of Lm are supported by SDM, corroborating the role of the Carpathians as a major refugial area. Our results, in combination with previous reports of extensive introgression of the major histocompatibility complex (MHC) genes, emphasize the complexity of historical gene exchange between Lm and Lv.     

Dispersal and selection mediate hybridization between a native and invasive species

Hybridization between native and non-native species has serious biological consequences, but our understanding of how dispersal and selection interact to influence invasive hybridization is limited. Here, we document the spread of genetic introgression between a native (Oncorhynchus clarkii) and invasive (Oncorhynchus mykiss) trout, and identify the mechanisms influencing genetic admixture. In two populations inhabiting contrasting environments, non-native admixture increased rapidly from 1984 to 2007 and was driven by surprisingly consistent processes. Individual admixture was related to two phenotypic traits associated with fitness: size at spawning and age of juvenile emigration. Fish with higher non-native admixture were larger and tended to emigrate at a younger age―relationships that are expected to confer fitness advantages to hybrid individuals. However, strong selection against non-native admixture was evident across streams and cohorts (mean selection coefficient against genotypes with non-native alleles (s) = 0.60; s.e. = 0.10). Nevertheless, hybridization was promoted in both streams by the continuous immigration of individuals with high levels of non-native admixture from other hybrid source populations. Thus, antagonistic relationships between dispersal and selection are mediating invasive hybridization between these fish, emphasizing that data on dispersal and natural selection are needed to fully understand the dynamics of introgression between native and non-native species.     

Admixture facilitates adaptation from standing variation in the European aspen (Populus tremula L.), a widespread forest tree

Adaptation to new environments can start from new mutations or from standing variation already present in natural populations. Whether admixture constrains or facilitates adaptation from standing variation is largely unknown, especially in ecological keystone or foundation species. We examined patterns of neutral and adaptive population divergence in Populus tremula L., a widespread forest tree, using mapped molecular genetic markers. We detected the genetic signature of postglacial admixture between a Western and an Eastern lineage of P. tremula in Scandinavia, an area suspected to represent a zone of postglacial contact for many species of animals and plants. Stringent divergence‐based neutrality tests provided clear indications for locally varying selection at the European scale. Six of 12 polymorphisms under selection were located less than 1 kb away from the nearest gene predicted by the Populus trichocarpa genome sequence. Few of these loci exhibited a signature of ‘selective sweeps’ in diversity‐based tests, which is to be expected if adaptation occurs primarily from standing variation. In Scandinavia, admixture explained genomic patterns of ancestry and the nature of clinal variation and strength of selection for bud set, a phenological trait of great adaptive significance in temperate trees, measured in a common garden trial. Our data provide a hitherto missing direct link between past range shifts because of climatic oscillations, and levels of standing variation currently available for selection and adaptation in a terrestrial foundation species.     

Loss of genetic diversity in isolated populations of an alpine endemic Pilosella alpicola subsp. ullepitschii: effect of long-term vicariance or long-distance dispersal?

Pilosella alpicola subsp. ullepitschii (Asteraceae) is a strictly allogamous, diploid Carpathian endemic. Its distribution range comprises two areas separated by about 600 km. While in the Western Carpathians (Slovakia and Poland) the taxon occurs in numerous sites, only four localities of man-made origin are known from the Eastern and Southern Carpathians (Romania). We used allozyme markers to test two likely possible scenarios for the origin of this disjunction: long distance dispersal and vicariance. Our data indicate a significant loss of genetic diversity in the isolated Eastern and Southern Carpathian populations in following genetic parameters (averaged per region): percentage of polymorphic loci (38.9% found in the Eastern and Southern Carpathians versus 58.3% in the Western Carpathians), allelic richness (1.4 vs. 1.6), expected heterozygosity (0.134 vs. 0.235), mean number of distinguishable multilocus genotypes (4.3 vs. 10.6) and proportion of distinguishable multilocus genotypes (0.34 vs. 0.68). Higher proportion of homozygous loci found in the Eastern and Southern Carpathian populations might indicate a higher rate of inbreeding due to non-random mating. We assume that these genetically depauperate populations have experienced a very strong genetic bottleneck, probably due to a founder effect. Although our data suggest that the long-distance dispersal model is most likely, more discriminate genetic markers should be used to test this further.     

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.     

Ancient and current gene flow between two distantly related Mediterranean oak species, Quercus suber and Q. ilex

Background and Aims

Quercus suber and Q. ilex are distantly related and their distributions partially overlap. They hybridize occasionally, but the complete replacement of Q. suber chloroplast DNA (cpDNA) by that of Q. ilex was identified in two specific geographical areas. The objective of this study was to determine whether the contrasting situation reflected current or recent geographical interspecies gene flow variation or was the result of ancient introgression.

Methods

cpDNA PCR-RFLPs (restriction fragment length polymorphisms) and variation at ten nuclear microsatellite loci were analysed in populations of each species, in 16 morphologically intermediate individuals and the progeny of several of them. Interspecies nuclear introgression was based on individual admixture rates using a Bayesian approach with no a priori species assignment, and on a maximum-likelihood (ML) method, using allele frequencies in the allopatric populations of each species as controls. Gene flow was compared specifically between populations located within and outside the specific areas.

Key Results

High interspecies nuclear genetic differentiation was observed, with twice the number of alleles in Q. ilex than in Q. suber. According to Bayesian assignment, approx. 1 % of individuals had a high probability of being F₁ hybrids, and bidirectional nuclear introgression affected approx. 4 % of individuals in each species. Hybrid and introgressed individuals were identified predominantly in mixed stands and may have a recent origin. Higher proportions including allospecific genes recovered from past hybridization were obtained using the ML method. Similar rates of hybridization and of nuclear introgression, partially independent of cpDNA interspecies transfer suggestive of gene filtering, were obtained in the populations located within and outside the areas of complete cpDNA replacement.

Conclusions

The results did not provide evidence for geographical variation in interspecies gene flow. In contrast, historical introgression is supported by palynological records and constitutes the more reliable origin of cpDNA replacement in specific regions.Key words: cpDNA PCR-RFLPs, nuclear microsatellite (nSSR) variation, hybridization, interspecies genetic introgression, Quercus suber, Quercus ilex     

Hybridization and low genetic diversity in the endangered Alabama red‐bellied turtle (Pseudemys alabamensis)

Pseudemys alabamensis is one of the most endangered freshwater turtle species in the United States due to its restricted geographic distribution in coastal Alabama and Mississippi. Populations of P. alabamensis are geographically isolated from one another by land and saltwater, which could act as barriers to gene flow. It is currently unknown how differentiated these populations are from one another and whether they have experienced reductions in population size. Previous work found morphological differences between Alabama and Mississippi populations, suggesting that they may be evolutionarily distinct. Other Pseudemys turtles such as P. concinna and P. floridana occur naturally within the same geographic area as P. alabamensis and are known to hybridize with each other. These more abundant species could threaten the unique genetic identity of P. alabamensis through introgression. In order to evaluate the endangered status of P. alabamensis and the level of hybridization with other species, we used mitochondrial and nuclear microsatellite markers to assess genetic variation within and among populations of P. alabamensis throughout its range and estimate admixture with co‐occurring Pseudemys species. In P. alabamensis, we found no variation in mitochondrial DNA and an excess of homozygosity in microsatellite data. Our results show genetic differentiation between Alabama and Mississippi populations of P. alabamensis, and low estimated breeding sizes and signs of inbreeding for two populations (Fowl River, Alabama and Biloxi, Mississippi). We also found evidence of admixture between P. alabamensis and P. concinna/P. floridana. Based on our results, P. alabamensis is highly endangered throughout its range and threatened by both low population sizes and hybridization. In order to improve the species’ chances of survival, focus should be placed on habitat preservation, maintenance of genetic diversity within both the Mississippi and Alabama populations, and routine population‐monitoring activities such as nest surveillance and estimates of recruitment.     

Variation in the chloroplast DNA of Swiss stone pine (Pinus cembra L.) reflects contrasting post-glacial history of populations from the Carpathians and the Alps

Aim To characterize the genetic structure and diversity of Pinus cembra L. populations native to two disjunct geographical areas, the Alps and the Carpathians, and to evaluate the rate of genetic differentiation among populations. Location The Swiss Alps and the Carpathians. Methods We screened 28 populations at three paternally inherited chloroplast simple sequence repeats (cpSSRs) for length variation in their mononucleotide repeats. Statistical analysis assessed haplotypic variation and fixation indices. Hierarchical analysis of molecular variance (AMOVA), Mantel test, spatial analysis of molecular variance (SAMOVA) and barrier analyses were applied to evaluate the geographical partitioning of genetic diversity across the species’ range. Results Haplotypic diversity was generally high throughout the natural range of P. cembra, with the mean value substantially higher in the Carpathians (H = 0.53) than in the Alps (H = 0.35). The isolated Carpathian populations showed the highest haplotype diversity among the populations originating from the High Tatras (Velka Studena Dolina) and South Carpathians (Retezat Mountains). AMOVA revealed that only 3% of the total genetic variation derived from genetic differentiation between the two mountain ranges. Differentiation among Carpathian populations was higher (F_ST = 0.19) than among Alpine populations (F_ST = 0.04). Low, but significant, correlation was found between the geographical and genetic distances among pairs of populations (r = 0.286, P < 0.001). SAMOVA results revealed no evident geographical structure of populations. barrier analysis showed the strongest differentiation in the eastern part of the species’ range, i.e. in the Carpathians. Main conclusions The populations of P. cembra within the two parts of the species’ range still share many cpDNA haplotypes, suggesting a common gene pool conserved from a previously large, continuous distribution range. Carpathian populations have maintained high haplotypic variation, even higher than Alpine populations, despite their small population sizes and spatial isolation. Based on our results, we emphasize the importance of the Carpathian populations of Swiss stone pine for conservation. These populations comprise private haplotypes and they may represent a particular legacy of the species’ evolutionary history.     

Population Genomics of Sub-Saharan Drosophila melanogaster: African Diversity and Non-African Admixture

Drosophila melanogaster has played a pivotal role in the development of modern population genetics. However, many basic questions regarding the demographic and adaptive history of this species remain unresolved. We report the genome sequencing of 139 wild-derived strains of D. melanogaster, representing 22 population samples from the sub-Saharan ancestral range of this species, along with one European population. Most genomes were sequenced above 25X depth from haploid embryos. Results indicated a pervasive influence of non-African admixture in many African populations, motivating the development and application of a novel admixture detection method. Admixture proportions varied among populations, with greater admixture in urban locations. Admixture levels also varied across the genome, with localized peaks and valleys suggestive of a non-neutral introgression process. Genomes from the same location differed starkly in ancestry, suggesting that isolation mechanisms may exist within African populations. After removing putatively admixed genomic segments, the greatest genetic diversity was observed in southern Africa (e.g. Zambia), while diversity in other populations was largely consistent with a geographic expansion from this potentially ancestral region. The European population showed different levels of diversity reduction on each chromosome arm, and some African populations displayed chromosome arm-specific diversity reductions. Inversions in the European sample were associated with strong elevations in diversity across chromosome arms. Genomic scans were conducted to identify loci that may represent targets of positive selection within an African population, between African populations, and between European and African populations. A disproportionate number of candidate selective sweep regions were located near genes with varied roles in gene regulation. Outliers for Europe-Africa F_ST were found to be enriched in genomic regions of locally elevated cosmopolitan admixture, possibly reflecting a role for some of these loci in driving the introgression of non-African alleles into African populations.     

Complex distribution patterns of di-, tetra-, and hexaploid cytotypes in the European high mountain plant Senecio carniolicus (Asteraceae)

DNA ploidy levels were estimated using DAPI-flow cytometry of silica-dried specimens of the European mountain plant Senecio carniolicus (Asteraceae), covering its entire distribution area in the Eastern Alps (77 populations, 380 individuals) and the Carpathians (five populations, 22 individuals). A complex pattern of ploidy level variation (2x, 4x, 5x, 6x, and 7x cytotypes) was found in this species, which has been considered uniformly hexaploid. Hexaploids predominated in the Eastern Alps and was the only cytotype found in the Carpathians, while odd ploidy levels (5x, 7x) constituted a small fraction of the samples (<1.3%). Tetraploids occurred in two disjunct areas, which correspond with putative Pleistocene refugia for silicicolous alpine plants. Diploids occurred in large portions of the Alps but were absent from areas most extensively glaciated in the past. Intrapopulational cytotype mixture was detected in 22 populations-the majority involving diploids and hexaploids-with intermediate ploidy levels mostly lacking, suggesting limited gene flow and the evolution of reproductive isolation. Significant and reproducible intracytotype variation in nuclear DNA content was observed. Higher genome size in western diploids might be due to ancient introgression with the closely related S. incanus or to different evolutionary pathways in the geographically separated diploids.     

Evolutionary History of the Grey-Faced Sengi,Rhynchocyon udzungwensis,from Tanzania: A Molecular and Species Distribution Modelling Approach

Rhynchocyon udzungwensis is a recently described and poorly understood sengi (giant elephant-shrew) endemic to two small montane forests in Southern Tanzania, and surrounded in lower forests by R. cirnei reichardi. In this study, we investigate the molecular genetic relationship between R. udzungwensis and R. c. reichardi, and the possible role that shifting species distributions in response to climate fluctuations may have played in shaping their evolutionary history. Rhynchocyon udzungwensis and R. c. reichardi individuals were sampled from five localities for genetic analyses. Three mitochondrial and two nuclear loci were used to construct species trees for delimitation and to determine whether introgression was detectable either from ancient or ongoing hybridization. All species-tree results show R. udzungwensis and R. c. reichardi as distinct lineages, though mtDNA shows evidence of introgression in some populations. Nuclear loci of each species were monophyletic, implying introgression is exclusively historical. Because we found evidence of introgression, we used distribution data and species distribution modelling for present, glacial, and interglacial climate cycles to predict how shifting species distributions may have facilitated hybridization in some populations. Though interpretations are affected by the limited range of these species, a likely scenario is that the mtDNA introgression found in eastern mid-elevation populations was facilitated by low numbers of R. udzungwensis that expanded into lowland heavily occupied R. c. reichardi areas during interglacial climate cycles. These results imply that relationships within the genus Rhynchocyon may be confounded by porous species boundaries and introgression, even if species are not currently sympatric.     

Genetic structure in northeastern populations of the Alpine newt (Triturus alpestris): evidence for post-Pleistocene differentiation

Genetic variation in 13 populations of the Alpine newt, Triturus alpestris, was assessed at the northeastern margin of its range (southern Poland). Variation at six microsatellite loci was scored in 354 newts, and two mitochondrial DNA fragments (c. 2000 bp) were sequenced in a subset of 27 individuals. Significant differences in allele frequencies and the presence of private alleles determined genetic units corresponding to three separate mountain ranges, i.e. the Carpathian, Sudetes and Holy Cross Mountains. F(ST)'s were three times greater in among than in within mountain range pairwise comparisons. An assignment test and pairwise F(ST)'s suggested relatively high levels of gene flow at the local level, although the Sudetes populations revealed some subtle structuring. Genetic variation was lower in the Carpathians and Holy Cross Mountains. The geographic pattern of mitochondrial DNA variation indicated that these newt populations originated from a single glacial refugium/founder population, and that the colonization of southern Poland took place in an easterly direction. The data show that substantial neutral variation and between group divergence has accumulated relatively quickly in these low-vagility organisms. The Alpine newt case exemplifies species history as a factor determining patterns of genetic diversity in marginal populations.     

Genetic structure of Hypochaeris uniflora (Asteraceae) suggests vicariance in the Carpathians and rapid post-glacial colonization of the Alps from an eastern Alpine refugium

Aim The range of the subalpine species Hypochaeris uniflora covers the Alps, Carpathians and Sudetes Mountains. Whilst the genetic structure and post‐glacial history of many high‐mountain plant taxa of the Alps is relatively well documented, the Carpathian populations have often been neglected in phylogeographical studies. The aim of the present study is to compare the genetic variation of the species in two major European mountain systems – the Alps and the Carpathians. Location Alps and Carpathians. Methods The genetic variation of 77 populations, each consisting of three plants, was studied using amplified fragment length polymorphism (AFLP). Results Neighbour joining and principal coordinate analyses revealed three well‐supported phylogeographical groups of populations corresponding to three disjunct geographical regions – the Alps and the western and south‐eastern Carpathians. Moreover, two further clusters could be distinguished within the latter mountain range, one consisting of populations from the eastern Carpathians and the second consisting of populations from the southern Carpathians. Populations from the Apuseni Mountains had an intermediate position between the eastern and southern Carpathians. The genetic clustering of populations into four groups was also supported by an analysis of molecular variance, which showed that most genetic variation (almost 46%) was found among these four groups. By far the highest within‐population variation was found in the eastern Carpathians, followed by populations from the southern and western Carpathians. Generally, the populations from the Alps were considerably less variable and displayed substantially fewer region‐diagnostic markers than those from the south‐eastern Carpathians. Although no clear geographical structure was found within the Alps, based on neighbour joining or principal coordinate analyses, some trends were obvious: populations from the easternmost part were genetically more variable and, together with those from the south‐western part, exhibited a higher proportion of rare AFLP fragments than populations in other areas. Moreover, the total number of AFLP fragments per population, the percentage of polymorphic loci and the proportion of rare AFLP fragments significantly decreased from east to west. Main conclusions Deep infraspecific phylogeographical gaps between the populations from the Alps and the western and south‐eastern Carpathians suggest the survival of H. uniflora in three separate refugia during the last glaciation. Our AFLP data provide molecular evidence for a long‐term geographical disjunction between the eastern and western Carpathians, previously suggested from the floristic composition at the end of 19th century. It is likely that Alpine populations survived the Last Glacial in the eastern part of the Alps, from where they rapidly colonized the rest of the Alps after the ice sheet retreated. Multiple founder effects may explain a gradual loss of genetic variation during westward colonization of the Alps.     

Interspecific gene flow in a multispecies oak hybrid zone in the Sierra Tarahumara of Mexico

Background and Aims

Interspecific gene flow can occur in many combinations among species within the genus Quercus, but simultaneous hybridization among more than two species has been rarely analysed. The present study addresses the genetic structure and morphological variation in a triple hybrid zone formed by Q. hypoleucoides, Q. scytophylla and Q. sideroxyla in north-western Mexico.

Methods

A total of 247 trees from ten reference and 13 presumed intermediate populations were characterized using leaf shape variation and geometric morphometrics, and seven nuclear microsatellites as genetic markers. Discriminant function analysis was performed for leaf shape variation, and estimates of genetic diversity and structure, and individual Bayesian genetic assignments were obtained.

Key Results

Reference populations formed three completely distinct groups according to discriminant function analysis based on the morphological data, and showed low, but significant, genetic differentiation. Populations from the zone of contact contained individuals morphologically intermediate between pairs of species in different combinations, or even among the three species. The Bayesian admixture analysis found that three main genetic clusters best fitted the data, with good correspondence of reference populations of each species to one of the genetic clusters, but various degrees of admixture evidenced in populations from the contact area.

Conclusions

The three oak species have formed a complex hybrid zone that is geographically structured as a mosaic, and comprising a wide range of genotypes, including hybrids between different species pairs, backcrosses and probable triple hybrids.     

High genetic diversity and distinct origin of recently fragmented Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.) populations along the Carpathians and the Pannonian Basin

Historical evolutionary events highly affect the modern-day genetic structure of natural populations. Scots pine (Pinus sylvestris L.), as a dominant tree species of the Eurasian taiga communities following the glacial cycles of the Pleistocene, has survived in small, scattered populations at the range limits of its south-eastern European distribution. In this study, we examined genetic relationships, genetic divergence and demographic history of peripheral populations from central-eastern Europe, the Carpathian Mountains and the Pannonian Basin. Four hundred twenty-one individuals from 20 populations were sampled and characterized with both nuclear and chloroplast simple sequence repeat (SSR) markers. Standard population genetic indices, the degree of genetic differentiation and spatial genetic structure were analysed. Our results revealed that peripheral Scots pine populations retained high genetic diversity despite the recently ongoing fragmentation and isolation of the persisting relict populations. Analysis of molecular variance (AMOVA) showed 7% among-population genetic differentiation, and there was no isolation by distance among the island-like occurrences. Genetic discontinuities with strong barriers (99–100% bootstrap support) were identified in the Carpathians. Based on both marker types, populations of the Western Carpathians were delimited from those inhabiting the Eastern Carpathians, and two main genetic lineages were traced that most probably originate from two main refugia. One refugium presumably existed in the region of the Eastern Alps with the Hungarian Plain, while the other was probably found in the Eastern Carpathians. These findings are supported by recent palynological records. The strongest genetic structure was revealed within the Romanian Carpathians on the basis of both marker types. With only some exceptions, no signs of recent bottlenecks or inbreeding were detected. However, Carpathian natural populations of Scots pine are highly fragmented and have a small census size, though they have not yet been affected by genetic erosion induced by isolation.     

The crested newt Triturus cristatus recolonized temperate Eurasia from an extra‐Mediterranean glacial refugium

We assess the role of the Carpathians as an extra‐Mediterranean glacial refugium for the crested newt Triturus cristatus. We combine a multilocus phylogeography (one mitochondrial protein‐coding gene, three nuclear introns, and one major histocompatibility complex gene) with species distribution modelling (projected on current and Last Glacial Maximum climate layers). All genetic markers consistently show extensive genetic variation within and genetic depletion outside the Carpathians. The species distribution model suggests that most of the current range was unsuitable at the Last Glacial Maximum, but a small suitable area remained in the Carpathians. Triturus cristatus dramatically expanded its postglacial range, colonizing much of temperate Eurasia from a glacial refugium in the Carpathians. Within the Carpathians, T. cristatus persisted in multiple geographically discrete regions, providing further support for a Carpathian ‘refugia within refugia’ scenario. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 574–587.     

Genetic structure in Pinus cembra from the Carpathian Mountains inferred from nuclear and chloroplast microsatellites confirms post-glacial range contraction and identifies introduced individuals

Genetic differentiation of scattered populations at neutral loci is characterized by genetic drift counteracted by the remaining gene flow. Populations of Pinus cembra in the Carpathian Mountains are isolated and restricted to island-like stands at high-elevation mountain ranges. In contrast, paleobotanical data suggest an extended early Holocene distribution of P. cembra in the Carpathians and its surrounding areas, which has contracted to the currently disjunct occurrences. We analyzed the genetic variation of 11 Carpathian populations of P. cembra at chloroplast and, in part newly developed, nuclear microsatellites. Both marker types revealed low levels of genetic differentiation and a lack of isolation by distance, reflecting the post-glacial retraction of the species to its current distribution. Stronger effects of genetic drift were implied by the higher genetic differentiation found for haploid chloroplast than for diploid nuclear markers. Moreover, we found no association between the values of population genetic differentiation for the two marker types. Several populations indicated recent genetic bottlenecks and inbreeding as a consequence of decline in population sizes. Moreover, we found individuals in two populations from the Rodnei Mountains that strikingly differed in assignment probabilities from the remaining specimens, suggesting that they had been introduced from a provenance outside the studied populations. Comparison with Eastern Alpine P. cembra and individuals of the closely related Pinus sibirica suggests that these individuals presumably are P. sibirica. Our study highlights the importance of the maintenance of sufficiently large local population sizes for conservation due to low connectivity between local occurrences.     

Population Genetic Structure of the Endangered Kaiser’s Mountain Newt,Neurergus kaiseri (Amphibia: Salamandridae)

Species often exhibit different levels of genetic structuring correlated to their environment. However, understanding how environmental heterogeneity influences genetic variation is difficult because the effects of gene flow, drift and selection are confounded. We investigated the genetic variation and its ecological correlates in an endemic and critically endangered stream breeding mountain newt, Neurergus kaiseri, within its entire range in southwestern Iran. We identified two geographic regions based on phylogenetic relationships using Bayesian inference and maximum likelihood of 779 bp mtDNA (D-loop) in 111 individuals from ten of twelve known breeding populations. This analysis revealed a clear divergence between northern populations, located in more humid habitats at higher elevation, and southern populations, from drier habitats at lower elevations regions. From seven haplotypes found in these populations none was shared between the two regions. Analysis of molecular variance (AMOVA) of N. kaiseri indicates that 94.03% of sequence variation is distributed among newt populations and 5.97% within them. Moreover, a high degree of genetic subdivision, mainly attributable to the existence of significant variance among the two regions is shown (θ_CT = 0.94, P = 0.002). The positive and significant correlation between geographic and genetic distances (r = 0.61, P = 0.002) following controlling for environmental distance suggests an important influence of geographic divergence of the sites in shaping the genetic variation and may provide tools for a possible conservation based prioritization policy for the endangered species.     

Genetic evidence of reproductive isolation in a remote enclave of Quercus pubescens in the presence of cross-fertile species

Peripheral populations may be crucial for understanding processes underlying adaptive genetic variation. Their evolution and ecology are driven by various genetic and demographic processes, such as selection, gene flow and bottleneck. Peripheral populations often experience a reduction in density resulting in the Allee effect. The presence of interfertile species increases the opportunity for hybridisation, which allows for a rescue from the Allee effect, but at the risk of genetic extinction through introgression. In this article we investigated a peripheral population of Quercus pubescens, a European tree species. The study population is located in Poland, several hundred kilometres northwards from the main species range. Due to geographic separation, the study population exists under strong pressure of introgression from potentially inter-fertile Q. petraea and Q. robur, which are the only common oaks in Poland. The intermediate morphology between typical Q. pubescens and a common oak species found in the study population supports the introgression hypothesis, which could be in line with the earlier studies of this species complex conducted in the main range of Q. pubescens. Alternatively, the intermediate morphology could reflect the founder effect or selection at an ecological extreme. We attempted to verify these hypotheses using microsatellites and a reference of common oak species. The results showed that the study population is genetically distinct from both Q. petraea and Q. robur. Additionally, the population is characterised by a low effective population size and limited gene dispersal. This suggests that the study population reveals strong reproductive isolation from common species, implying alternative sources of atypical morphology.     

Morphometric and RAPD study of theMelampyrum sylvaticum group in the Sudeten, the Alps and Carpathians

TheMelampyrum sylvaticum group is a heterogeneous group at the inter- and infra-specific level. A wide range of morphological characters was examined on specimens collected for this study. The corolla size, the corolla colour and the anther length are considered the most important morphological characters at the interspecific taxonomic level. The morphological and molecular variation of theMelampyrum sylvaticum group in the Sudeten, Alps and Carpathians was analyzed. The morphometric study of European populations ofMelampyrum sylvaticum group partly clarified the pattern of the variation of selected characters in this region. The RAPD analysis manifests a very similar trend of the population grouping. The combined analysis of morphological and molecular data gives the most explicit results. Central European yellow flowering populations ofM. sylvaticum group form two distinctive groups. The first one is an exclusive type of the Alps and of the Hercynian Mountains (except the Sudeten). The second group has its centre of distribution in the eastern part of the Carpathians. This type was described asMelampyrum herbichii from the present Ukrainian Carpathians and was regarded to be endemic to the Eastern and Southern Carpathians. Populations from the Western Carpathians and Sudeten Mts. are polymorphic. They seem to be closer toM. herbichii based on the RAPD markers, whereas the morphology of most populations from these regions is closer toM. sylvaticum s.str. The bract shape seems to be important for discrimination between both groups of populations along with the flower characters and a modest ecological differentiation. The Eastern CarpathianMelampyrum saxosum with white corolla is very close toM. herbichii based on the studied morphological characters.