Detecting a hierarchical genetic population structure: the case study of the Fire Salamander (Salamandra salamandra) in Northern Italy

The multistep method here applied in studying the genetic structure of a low dispersal and philopatric species, such as the Fire Salamander Salamandra salamandra, was proved to be effective in identifying the hierarchical structure of populations living in broad‐leaved forest ecosystems in Northern Italy. In this study, 477 salamander larvae, collected in 28 sampling populations (SPs) in the Prealpine and in the foothill areas of Northern Italy, were genotyped at 16 specie‐specific microsatellites. SPs showed a significant overall genetic variation (Global F_ST = 0.032, P < 0.001). The genetic population structure was assessed by using STRUCTURE 2.3.4. We found two main genetic groups, one represented by SPs inhabiting the Prealpine belt, which maintain connections with those of the Eastern foothill lowland (PEF), and a second group with the SPs of the Western foothill lowland (WF). The two groups were significantly distinct with a Global F_ST of 0.010 (P < 0.001). While the first group showed a moderate structure, with only one divergent SP (Global F_ST = 0.006, P < 0.001), the second group proved more structured being divided in four clusters (Global F_ST = 0.017, P = 0.058). This genetic population structure should be due to the large conurbations and main roads that separate the WF group from the Prealpine belt and the Eastern foothill lowland. The adopted methods allowed the analysis of the genetic population structure of Fire Salamander from wide to local scale, identifying different degrees of genetic divergence of their populations derived from forest fragmentation induced by urban and infrastructure sprawl.     

Landscape variability explains spatial pattern of population structure of northern pike (Esox lucius) in a large fluvial system

A growing number of studies have been investigating the influence of contemporary environmental factors on population genetic structure, but few have addressed the issue of spatial patterns in the variable intensity of factors influencing the extent of population structure, and particularly so in aquatic ecosystems. In this study, we document the landscape genetics of northern pike (Esox lucius), based on the analysis of nearly 3000 individuals from 40 sampling sites using 22 microsatellites along the Lake Ontario – St. Lawrence River system (750 km) that locally presents diverse degrees of interannual water level variation. Genetic structure was globally very weak (F_ST = 0.0208) but spatially variable with mean level of differentiation in the upstream section of the studied area being threefold higher (F_ST = 0.0297) than observed in the downstream sector (F_ST = 0.0100). Beside interannual water level fluctuation, 19 additional variables were considered and a multiple regression on distance matrices model (R² = 0.6397, P < 0.001) revealed that water masses (b = 0.3617, P < 0.001) and man‐made dams (b = 0.4852, P < 0.005) reduced genetic connectivity. Local level of interannual water level stability was positively associated to the extent of genetic differentiation (b = 0.3499, P < 0.05). As water level variation impacts on yearly quality and localization of spawning habitats, our study illustrates how temporal variation in local habitat availability, caused by interannual water level fluctuations, may locally decrease population genetic structure by forcing fish to move over longer distances to find suitable habitat. This study thus represents one of the rare examples of how environmental fluctuations may influence spatial variation in the extent of population genetic structure within a given species.     

Limited connectivity and a phylogeographic break characterize populations of the pink anemonefish,Amphiprion perideraion,in the Indo‐Malay Archipelago: inferences from a mitochondrial and microsatellite loci

To enhance the understanding of larval dispersal in marine organisms, species with a sedentary adult stage and a pelagic larval phase of known duration constitute ideal candidates, because inferences can be made about the role of larval dispersal in population connectivity. Members of the immensely diverse marine fauna of the Indo‐Malay Archipelago are of particular importance in this respect, as biodiversity conservation is becoming a large concern in this region. In this study, the genetic population structure of the pink anemonefish, Amphiprion perideraion, is analyzed by applying 10 microsatellite loci as well as sequences of the mitochondrial control region to also allow for a direct comparison of marker‐derived results. Both marker systems detected a strong overall genetic structure (Φ_ST = 0.096, P < 0.0001; mean D_est = 0.17; F_ST = 0.015, P < 0.0001) and best supported regional groupings (Φ_CT = 0.199 P < 0.0001; F_CT = 0.018, P < 0.001) that suggested a differentiation of the Java Sea population from the rest of the archipelago. Differentiation of a New Guinea group was confirmed by both markers, but disagreed over the affinity of populations from west New Guinea. Mitochondrial data suggest higher connectivity among populations with fewer signals of regional substructure than microsatellite data. Considering the homogenizing effect of only a few migrants per generation on genetic differentiation between populations, marker‐specific results have important implications for conservation efforts concerning this and similar species.     

Evidence for adaptive phenotypic differentiation in Baltic Sea sticklebacks

The evidence for adaptive phenotypic differentiation in mobile marine species remains scarce, partly due to the difficulty of obtaining quantitative genetic data to demonstrate the genetic basis of the observed phenotypic differentiation. Using a combination of phenotypic and molecular genetic approaches, we elucidated the relative roles of natural selection and genetic drift in explaining lateral plate number differentiation in threespine sticklebacks (Gasterosteus aculeatus) across the entire Baltic Sea basin (approximately 392 000 km²). We found that phenotypic differentiation (P_ST = 0.213) in plate number exceeded that in neutral markers (F_ST = 0.008), suggesting an adaptive basis for the observed differentiation. Because a close correspondence was found between plate phenotype and genotype at a quantitative trait loci (QTL; STN381) tightly linked to the gene (Ectodysplasin) underlying plate variation, the evidence for adaptive differentiation was confirmed by comparison of F_ST at the QTL (F_STQ = 0.089) with F_ST at neutral marker loci. Hence, the results provide a comprehensive demonstration of adaptive phenotypic differentiation in a high‐gene‐flow marine environment with direct, rather than inferred, verification for the genetic basis of this differentiation. In general, the results illustrate the utility of P_ST–F_ST–F_STQ comparisons in uncovering footprints of natural selection and evolution and add to the growing evidence for adaptive genetic differentiation in high‐gene‐flow marine environments, including that of the relatively young Baltic Sea.     

Microsatellite DNA markers indicate three genetic lineages in East Asian indigenous goat populations

The genetic differentiation and phylogenetic relationships of 18 indigenous goat populations from seven East Asian countries were analysed based on data obtained from 26 microsatellite DNA markers. The mean number of alleles (MNA) per population ranged from 2.5 to 7.6, with an average of 5.8. Genetic variability estimated from MNA and heterozygosity (H_E and H_O) were relatively low in coastal and island populations. A heterozygous deficiency within populations (F_IS = 0.054, P < 0.001) and total inbreeding (F_IT = 0.181, P < 0.01) were observed, and genetic differentiation in the populations (F_ST) was 13.4%. The results of Bayesian model‐based clustering and a neighbour‐joining tree based on Nei's genetic distance showed that Asian goat populations could be subdivided into at least the following three genetic clusters: East Asian, Southeast Asian and Mongolian. These results are in close accordance with conventional morphological and geographical classifications and migration history.     

Emergent patterns of population genetic structure for a coral reef community

What shapes variation in genetic structure within a community of codistributed species is a central but difficult question for the field of population genetics. With a focus on the isolated coral reef ecosystem of the Hawaiian Archipelago, we assessed how life history traits influence population genetic structure for 35 reef animals. Despite the archipelago's stepping stone configuration, isolation by distance was the least common type of genetic structure, detected in four species. Regional structuring (i.e. division of sites into genetically and spatially distinct regions) was most common, detected in 20 species and nearly in all endemics and habitat specialists. Seven species displayed chaotic (spatially unordered) structuring, and all were nonendemic generalist species. Chaotic structure also associated with relatively high global F_ST. Pelagic larval duration (PLD) was not a strong predictor of variation in population structure (R² = 0.22), but accounting for higher F_ST values of chaotic and invertebrate species, compared to regionally structured and fish species, doubled the power of PLD to explain variation in global F_ST (adjusted R² = 0.50). Multivariate correlation of eight species traits to six genetic traits highlighted dispersal ability, taxonomy (i.e. fish vs. invertebrate) and habitat specialization as strongest influences on genetics, but otherwise left much variation in genetic traits unexplained. Considering that the study design controlled for many sampling and geographical factors, the extreme interspecific variation in spatial genetic patterns observed for Hawaìi marine species may be generated by demographic variability due to species‐specific abundance and migration patterns and/or seascape and historical factors.     

Genetic connectivity among swarming sites in the wide ranging and recently declining little brown bat (Myotis lucifugus)

Characterizing movement dynamics and spatial aspects of gene flow within a species permits inference on population structuring. As patterns of structuring are products of historical and current demographics and gene flow, assessment of structure through time can yield an understanding of evolutionary dynamics acting on populations that are necessary to inform management. Recent dramatic population declines in hibernating bats in eastern North America from white‐nose syndrome have prompted the need for information on movement dynamics for multiple bat species. We characterized population genetic structure of the little brown bat, Myotis lucifugus, at swarming sites in southeastern Canada using 9 nuclear microsatellites and a 292‐bp region of the mitochondrial genome. Analyses of F_ST, Φ_ST, and Bayesian clustering (STRUCTURE) found weak levels of genetic structure among swarming sites for the nuclear and mitochondrial genome (Global F_ST = 0.001, P < 0.05, Global Φ_ST = 0.045, P < 0.01, STRUCTURE K = 1) suggesting high contemporary gene flow. Hierarchical AMOVA also suggests little structuring at a regional (provincial) level. Metrics of nuclear genetic structure were not found to differ between males and females suggesting weak asymmetries in gene flow between the sexes. However, a greater degree of mitochondrial structuring does support male‐biased dispersal long term. Demographic analyses were consistent with past population growth and suggest a population expansion occurred from approximately 1250 to 12,500 BP, following Pleistocene deglaciation in the region. Our study suggests high gene flow and thus a high degree of connectivity among bats that visit swarming sites whereby mainland areas of the region may be best considered as one large gene pool for management and conservation.     

Microsatellite variation, population structure, and bottlenecks in the threatened copperbelly water snake

Habitat loss and isolation is pervasive in the Midwest U.S. Wetlands are experiencing particularly dramatic declines, yet there is a paucity of information on the genetic impacts of these losses to obligate wetland vertebrates. We quantified the genetic variation of extant populations of a shallow wetland specialist and evaluated potential reductions in population size (i.e. bottlenecks) using seven polymorphic microsatellite DNA markers. We analyzed 228 copperbelly water snakes (Nerodia erythrogaster neglecta), representing populations from three states. Moderate genetic differentiation exists among all three regions (F _ST = 0.12, P < 0.001), with evidence for low levels of differentiation within the federally protected Ohio region (F _ST = 0.025, P = 0.007), and moderate to strong differentiation within the Indiana region (F _ST = 0.23, P < 0.001). Furthermore, Bayesian clustering (i.e. STRUCTURE) supports the separation of the Indiana sites, both from each other and from all other sampling sites. However, it does not support the separation of the Ohio sites from the Kentucky sites. Differentiation among sampling sites did not appear to be related to geographic distance, but rather depended on the quality of terrestrial corridors used for dispersal. Mode shifts in allele frequencies and excess heterozygosity tests were negative, while M-ratio tests were nearly all positive, indicating the likelihood of historical rather than contemporary population bottlenecks. However, potential subspecific intergradation in the Kentucky region may have artificially lowered the M-ratio, and we suggest caution when using the M-ratio approach if intergradation is suspected. Our results have conservation implications for wetland management and management of the copperbelly populations, and emphasizes the importance of protecting wetland complexes.     

Mitochondrial DNA diversity of the vulnerable Chinese Egret (Egretta eulophotes) from China

The genetic diversity and population structure of the vulnerable Chinese Egret (Egretta eulophotes) were surveyed in the present study from three archipelagoes that cover the most southerly to the very northerly parts of the Chinese distribution range of this species, using a 433-bp fragment of the mitochondrial control region (CR). Among 90 individual samples, 31 different haplotypes were defined by 30 polymorphic sites. Overall haplotype diversity, nucleotide diversity and mean sequence divergence (p-distance) of this egret were 0.920, 0.0088 and 1.11%, respectively. NJ tree and parsimony network for the CR haplotypes of the Chinese Egret showed little genetic structure, and analysis of molecular variance indicated low but significant genetic differentiation (haplotype-based Φ_ST = 0.03267, P < 0.05 and distance-based Φ_ST = 0.04194, P < 0.05) among populations. The significant Fu’s F _S tests (Fu’s F _S  = −16.946, P < 0.01) and mismatch distribution analysis (τ = 4.463, SSD = 0.0081, P = 0.12) suggested that the low genetic differentiation and little geographical structure of the genetic differentiation might be explained by the population expansion. The Mantel test (haplotype-based F _ST, r = 0.639, P = 0.34 and distance-based F _ST, r = 0.947, P = 0.15) suggest that the significant genetic differentiation among populations was likely due to isolation by distance.     

Isolation by Time During an Arctic Phytoplankton Spring Bloom

The arctic phytoplankton spring bloom, which is often diatom‐dominated, is a key event that provides the high latitude communities with a fundamental flux of organic carbon. During a bloom, phytoplankton may increase its biomass by orders of magnitude within days. Yet, very little is known about phytoplankton bloom dynamics, including for example how blooming affects genetic composition and diversity of a population. Here, we quantified the genetic composition and temporal changes of the diatom Fragilariopsis cylindrus, which is one of the most important primary producers in the Arctic, during the spring bloom in western Greenland, using 13 novel microsatellite markers developed for this study. We found that genetic differentiation (quantified using sample‐specific F_ST) decreased between time points as the bloom progressed, with the most drastic changes in F_ST occurring at the start of the bloom; thus the genetic structure of the bloom is characterized by isolation by time. There was little temporal variation in genetic diversity throughout the bloom (mean H_E = 0.57), despite marked fluctuations in F. cylindrus cell concentrations and the temporal change in sample‐specific F_ST. On the basis of this novel pattern of genetic differentiation, we suggest that blooming behavior may promote genetic diversity of a phytoplankton population.     

Non‐timber Forest Product Harvest does not Affect the Genetic Diversity of a Tropical Tree Despite Negative Effects on Population Fitness

The level of genetic diversity in a population can affect ecological processes and plant responses to disturbance. In turn, disturbance can alter population genetic diversity and structure. Populations in fragmented and logged habitats often show reduced genetic diversity and increased inbreeding and differentiation. Long‐term harvesting of wild plants (for foliage, bark, and roots), can affect population genetic diversity by altering individual fitness and genetic contribution. Our understanding of these changes in genetic diversity due to the harvesting of plant organs is still limited. We used nine microsatellite markers to study the effect of long‐term bark and foliage harvest by Fulani people on the genetic diversity and structure of 12 populations of African mahogany (Khaya senegalensis) in Benin. We sampled 20 individuals in each population to test the effect of harvesting. For each population, we divided the samples equally between seedling and adults to test if the effects are stronger in seedlings. We found moderate genetic diversity (H_e = 0.53 ± 0.04) and weak but significant differentiation among local populations (F_ST = 0.043, P < 0.001). There was no significant effect of harvest on genetic diversity or structure, although previous work found significant negative effects of harvest on the reproduction of adults, offspring density, and population fitness. Our results suggest that demographic responses to disturbance precede a detectable genetic response. Future studies should focus on using parentage analysis to test if genotypes of harvested parents are directly represented in the offspring populations.     

Effect of the Aegean Sea barrier between Europe and Asia on differentiation in Juniperus drupacea (Cupressaceae)

Juniperus drupacea is an eastern Mediterranean mountain tree with a disjunct geographical range. We hypothesized that this disjunct occurrence (the Peloponnese in Europe and the Taurus and Lebanon Mountains in Asia) should be reflected in the patterns of genetic and morphological diversity and differentiation. Nuclear microsatellite markers (nSSR) and biometric variables of the cones and seeds were examined on material sampled from four populations in Europe and eight in Asia. The Asian populations were characterized by a higher level of genetic diversity than the European populations. The genetic differentiation among populations was moderate but significant (F_ST = 0.101, P < 0.001). According to the clustering performed with BAPS, six genetically and geographically groups of populations were found: I and II from the Peloponnese; III from the Taurus Mountains; IV and V from the Anti‐Taurus Mountains; and VI from the Lebanon Mountains. The level of genetic differentiation among these six groups (4.30%, P = 0.012) probably reflects long‐lasting genetic isolation during the Pleistocene, as limited genetic admixture was found. In accordance with genetic analysis, the biometric investigations indicated a high level of morphological divergence between the European and Asian populations of the species, with further differentiation between the populations from the Taurus and Lebanon Mountains.     

Drift happens: Molecular genetic diversity and differentiation among populations of jewelweed (Impatiens capensis Meerb.) reflect fragmentation of floodplain forests

Landscape features often shape patterns of gene flow and genetic differentiation in plant species. Populations that are small and isolated enough also become subject to genetic drift. We examined patterns of gene flow and differentiation among 12 floodplain populations of the selfing annual jewelweed (Impatiens capensis Meerb.) nested within four river systems and two major watersheds in Wisconsin, USA. Floodplain forests and marshes provide a model system for assessing the effects of habitat fragmentation within agricultural/urban landscapes and for testing whether rivers act to genetically connect dispersed populations. We generated a panel of 12,856 single nucleotide polymorphisms and assessed genetic diversity, differentiation, gene flow, and drift. Clustering methods revealed strong population genetic structure with limited admixture and highly differentiated populations (mean multilocus F_ST = 0.32, F_ST’ = 0.33). No signals of isolation by geographic distance or environment emerged, but alleles may flow along rivers given that genetic differentiation increased with river distance. Differentiation also increased in populations with fewer private alleles (R² = 0.51) and higher local inbreeding (R² = 0.22). Populations varied greatly in levels of local inbreeding (F_IS = 0.2–0.9) and F_IS increased in more isolated populations. These results suggest that genetic drift dominates other forces in structuring these Impatiens populations. In rapidly changing environments, species must migrate or genetically adapt. Habitat fragmentation limits both processes, potentially compromising the ability of species to persist in fragmented landscapes.     

High degree of genetic differentiation in marine three‐spined sticklebacks (Gasterosteus aculeatus)

Populations of widespread marine organisms are typically characterized by a low degree of genetic differentiation in neutral genetic markers, but much less is known about differentiation in genes whose functional roles are associated with specific selection regimes. To uncover possible adaptive population divergence and heterogeneous genomic differentiation in marine three‐spined sticklebacks (Gasterosteus aculeatus), we used a candidate gene‐based genome‐scan approach to analyse variability in 138 microsatellite loci located within/close to (<6 kb) functionally important genes in samples collected from ten geographic locations. The degree of genetic differentiation in markers classified as neutral or under balancing selection—as determined with several outlier detection methods—was low (F_ST = 0.033 or 0.011, respectively), whereas average F_ST for directionally selected markers was significantly higher (F_ST = 0.097). Clustering analyses provided support for genomic and geographic heterogeneity in selection: six genetic clusters were identified based on allele frequency differences in the directionally selected loci, whereas four were identified with the neutral loci. Allelic variation in several loci exhibited significant associations with environmental variables, supporting the conjecture that temperature and salinity, but not optic conditions, are important drivers of adaptive divergence among populations. In general, these results suggest that in spite of the high degree of physical connectivity and gene flow as inferred from neutral marker genes, marine stickleback populations are strongly genetically structured in loci associated with functionally relevant genes.     

Genetic structure of the Painted Bunting and its implications for conservation of migratory populations

The Painted Bunting Passerina ciris is a Neotropical songbird which breeds primarily in the USA during the summer and migrates to Mexico, Central America, southern Florida and the Caribbean over the winter. Male Painted Buntings are brightly coloured, which makes them highly sought after as pets, particularly in Mexico, Central America and Europe. We used short sequence repeats (microsatellite DNA) to investigate the population genetic structure of the Painted Bunting and its implications in conservation management of migratory populations. We found a detectable level of population differentiation as revealed by pairwise F_ST and R_ST comparisons and Bayesian clustering analyses, with strong support for differentiation between eastern and western Painted Buntings (e.g. Oklahoma and Georgia F_ST = 0.1; P = 0.005; R_ST = 0.18; P = 0.04) in accordance with previous mitochondrial DNA analysis. We recovered additional support for two sub‐groups within the western clade. While linking migrant songbirds captured outside of the USA to their breeding populations remains a challenge, we show that natural levels of population genetic differentiation can be detected via microsatellite DNA markers and exploited in migratory connectivity studies. We also demonstrate the potential utility of our low‐cost markers for population identification of birds recovered from the pet trade by screening a small subset of samples (n = 5) collected as part of wildlife tracking. We discuss the implications of our results for future efforts to understand patterns of population decline in Painted Buntings more generally, as well as how we might expand this methodology to combat illegal pet‐trade activity in this and other songbird species.     

Sequence Polymorphism and Geographical Variation at a Positively Selected MHC-DRB Gene in the Finless Porpoise (Neophocaena phocaenoides): Implication for Recent Differentiation of the Yangtze Finless Porpoise?

Sequence polymorphism at the MHC class II DRB locus was investigated in three finless porpoise (Neophocaena phocaenoides) populations in Chinese waters. Intragenic recombination and strong positive selection were the main forces in generating sequence diversity in the DRB gene. MHC sequence diversity changed significantly along the study period. Significant decrease in heterozygosity and lost alleles have been detected in the Yangtze River population and South China Sea population since 1990. Furthermore, there is a trend of increasing population differentiation over time. Especially, the genetic differentiation between the Yangtze River population and the Yellow Sea population was very low prior to 1990 (F _ST = 0.036, P = 0.009), but became very significant after 1990 (F _ST = 0.134, P < 0.001), suggesting a recent augmentation of genetic differentiation between both populations probably in a relatively short-term period. Porpoises from the Yangtze River displayed divergent frequencies of shared and private alleles from those displayed by two marine populations, which suggest that the former riverine population has been under a different selection regime (characteristic of a fresh water environment) than that of its marine counterparts.     

Is life history a barrier to dispersal? Contrasting patterns of genetic differentiation along an oceanographically complex coast

Extreme variation in early life‐history strategies is considered a moderately good predictor of genetic subdivision and hence dispersal for a range of marine species. In reality, however, a good deal of population differentiation must reflect historical effects, more subtle variation in life histories, and, particularly, the interaction of larvae with oceanographic processes. Using a combination of allozyme and microsatellite markers, we show that the large‐scale genetic structure of populations of three species (direct and planktonically developing cushion stars and a planktonic developing sea anemone that is also asexually viviparous) varies consistently, in line with the predicted capacity for dispersal within three geographic regions. We detected high levels of genetic subdivision for the direct developing cushion star (F_ST = 0.6), low levels for the planktonically developing cushion star (F_ST = 0.009), and intermediate levels for the sexual/asexual sea anmone (F_ST = 0.19). These patterns are exhibited despite the highly variable patterns of current movement and the presence of biogeographic barriers. Our results suggest that, although there is large scale genetic differentiation for two species, patterns of population connectivity are remarkably consistent within major regions and do not reflect variation in major oceanographic processes or genetic discontinuity coincident with biogeographic boundaries. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 106–116.     

Novel Y‐chromosome short tandem repeats in Sus scrofa and their variation in European wild boar and domestic pig populations

Y‐chromosome markers are important tools for studying male‐specific gene flow within and between populations, hybridization patterns and kinship. However, their use in non‐human mammals is often hampered by the lack of Y‐specific polymorphic markers. We identified new male‐specific short tandem repeats (STRs) in Sus scrofa using the available genome sequence. We selected four polymorphic loci (5–10 alleles per locus), falling in one duplicated and two single‐copy regions. A total of 32 haplotypes were found by screening 211 individuals from eight wild boar populations across Europe and five domestic pig populations. European wild boar were characterized by significantly higher levels of haplotype diversity compared to European domestic pigs (H_D = 0.904 ± 0.011 and H_D = 0.491 ± 0.077 respectively). Relationships among STR haplotypes were investigated by combining them with single nucleotide polymorphisms at two linked genes (AMELY and UTY) in a network analysis. A differentiation between wild and domestic populations was observed (F_ST = 0.229), with commercial breeds sharing no Y haplotype with the sampled wild boar. Similarly, a certain degree of geographic differentiation was observed across Europe, with a number of local private haplotypes and high diversity in northern populations. The described Y‐chromosome markers can be useful to track male inheritance and gene flow in wild and domestic populations, promising to provide insights into evolutionary and population genetics in Sus scrofa.     

Habitat fragmentation influences genetic diversity and differentiation: Fine‐scale population structure of Cercis canadensis (eastern redbud)

Forest fragmentation may negatively affect plants through reduced genetic diversity and increased population structure due to habitat isolation, decreased population size, and disturbance of pollen‐seed dispersal mechanisms. However, in the case of tree species, effective pollen‐seed dispersal, mating system, and ecological dynamics may help the species overcome the negative effect of forest fragmentation. A fine‐scale population genetics study can shed light on the postfragmentation genetic diversity and structure of a species. Here, we present the genetic diversity and population structure of Cercis canadensis L. (eastern redbud) wild populations on a fine scale within fragmented areas centered around the borders of Georgia–Tennessee, USA. We hypothesized high genetic diversity among the collections of C. canadensis distributed across smaller geographical ranges. Fifteen microsatellite loci were used to genotype 172 individuals from 18 unmanaged and naturally occurring collection sites. Our results indicated presence of population structure, overall high genetic diversity (H_E = 0.63, H_O = 0.34), and moderate genetic differentiation (F_ST = 0.14) among the collection sites. Two major genetic clusters within the smaller geographical distribution were revealed by STRUCTURE. Our data suggest that native C. canadensis populations in the fragmented area around the Georgia–Tennessee border were able to maintain high levels of genetic diversity, despite the presence of considerable spatial genetic structure. As habitat isolation may negatively affect gene flow of outcrossing species across time, consequences of habitat fragmentation should be regularly monitored for this and other forest species. This study also has important implications for habitat management efforts and future breeding programs.     

Temporal shifts of DNA‐microsatellite allele profiles in roe deer (Capreolus capreolus L.) within three decades

DNA‐microsatellite polymorphism (four loci) was studied in 56 male roe deer (Capreolus capreolus) from a 900‐ha hunting territory in the Vosges du Nord Mountains (France), culled over 34 years (1956–1990). Changed allele frequencies at two loci within this period, and increased allelic diversity, were traced to a phase of reduced population density and subsequent immigration. Decadic population samples collected within 900‐ha were distinguished by higher genetic variability measures than were certain geographical samples across Central Europe (4–900 km). On average, the decadic cohorts were distinguished by a gene diversity index of G_ST = 0.0286, and a genetic distance of D = 0.0938, which reflect 54% (G_ST) and 69% (D) of the respective geographic (350 km) differentiation indices of roe deer in Central Europe. The importance of demography and population ecology effects for microevolution in a large mammal is demonstrated, as is the risk of artefact by composing population samples of deer over several years. Population genetic screening should cover various demes of roe deer from the same general region, and be based on many unlinked polymorphic loci, to minimize the distorting effects of genetic dynamics at the small spatial scale.