Genetic structure within and between island populations of the flightless cormorant (Phalacrocorax harrisi)

We assessed colony- and island-level genetic differentiation for the flightless cormorant ( Phalacrocorax harrisi ), an endangered Galápagos endemic that has one of the most limited geographical distributions of any seabird, consisting of only two adjacent islands. We screened 223 individuals from both islands and nine colonies at five microsatellite loci, recovering 23 alleles. We found highly significant genetic differentiation throughout the flightless cormorant's range on Fernandina and Isabela Islands (global F _ST = 0.097; P  < 0.0003) both between islands (supported by Bayesian analyses, F _ST and R _ST values) and within islands (supported only by F _ST and R _ST values). An overall pattern of isolation-by-distance was evident throughout the sampled range ( r =  0.4169, one-sided P  ≤ 0.02) and partial Mantel tests of this relationship confirmed that ocean is a dispersal barrier ( r =  0.500, one-sided P  ≤ 0.003), especially across the 5-km gap between the two islands. The degree of detected genetic differentiation among colonies is surprising, given the flightless cormorant's limited range, and suggests a role for low vagility, behavioural philopatry, or both to limit dispersal where physical barriers are absent. We argue that this population should be managed as at least two genetic populations to better preserve the species-level genetic diversity, but, for demographic reasons, advocate the continued conservation of all breeding colonies.     

Ancestry and divergence of subtropical montane forest isolates: molecular biogeography of the genus Abies (Pinaceae) in southern México and Guatemala

The genus Abies has a complex history in southern México and Guatemala. In this region, four closely related species, Abies flinckii , A. guatemalensis , A. hickelii , and A. religiosa , are distributed in fragmented and isolated montane populations. Range-wide genetic variation was investigated across species using cytoplasmic DNA markers with contrasted inheritance. Variation at two maternally inherited mitochondrial DNA markers was low. All species shared two of the nine mitotypes detected, while the remaining seven mitochondrial DNA types were restricted to a few isolated stands. Mitochondrial genetic differentiation across taxa was high ( G _ST = 0.933), it was not related to the taxonomic identity ( amova ; P  > 0.05) of the populations, and it was not phylogeographically structured ( G _ST ≈  N _ST). In contrast, variation at three paternally inherited chloroplast DNA microsatellites was high. Chloroplast genetic differentiation was lower ( G _ST = 0.402; R _ST = 0.547) than for mitochondrial DNA, but it was significantly related to taxonomy ( amova ; P  < 0.001), and exhibited a significant phylogeographical structure ( G _ST <  R _ST). Different analyses of population structure indicated that A. flinckii was the most divergent taxon, while the remaining three species formed a relatively homogeneous group. However, a small number of the populations of these three taxa, all located at the limits of their respective ranges or in the Transverse Volcanic Belt, diverged from this main cluster. These trends suggest that the Mesoamerican Abies share a recent common ancestor and that their divergence and speciation is mainly driven by genetic drift and isolation during the warm interglacial periods.     

Understanding population structure and historical demography in a conservation context: population genetics of an endangered fern

The construction of the world's largest hydroelectric scheme across the Yangtze River, the Three Gorges Dams (TGD), in the centre of a southern-central Chinese biodiversity hot spot, the Three Gorges Reservoir Area (TGRA), has attracted international concern and conservation action. To examine whether landscape changes to date have impacted regional flora, and to establish long-term monitoring baselines, we assessed the distribution and dynamics of an endangered and TGRA endemic fern, Adiantum reniforme var. sinense . For eight nuclear microsatellites, high levels of genetic diversity ( H _E = 0.653–0.781) and slightly elevated inbreeding ( F _IS = 0.077–0.197) were found across 13 surveyed populations. The population history of this fern is characterized by a balance of gene flow and genetic drift, where historical dispersal, inferred from coalescent ( F =  0.129) and genetic differentiation ( F _ST = 0.094 and R _ST = 0.180) approaches, is moderate, reflecting an isolation by distance relationship. Importantly, most populations exhibited mutation-drift disequilibrium, suggesting a recent population decline, which is congruent with the known demographic history of the species following dam-related activities. Based on these results, populations of A. reniforme var. sinense are expected to lose genetic diversity and increase genetic structure as dam-related activities decrease size and increase genetic isolation of remnants.     

Population divergence in the amphicarpic species Amphicarpaea edgeworthii Benth. (Fabaceae): microsatellite markers and leaf morphology

Comparative analyses of the genetic differentiation in microsatellite markers ( F _ST) and leaf morphology characters ( Q _ST) of Amphicarpaea edgeworthii Benth. were conducted to gain insight into the roles of random processes and natural selection in the population divergence. Simple sequence repeat analyses on 498 individuals of 19 natural populations demonstrate that a significant genetic differentiation occurs among populations (mean F _ST = 0.578), and A. edgeworthii is a highly self-fertilized species (mean selfing rate s  = 0.989). The distribution pattern of genetic diversity in this species shows that central populations possess high genetic diversity (e.g. population WL with H _E = 0.673 and population JG with H _E = 0.663), whereas peripheral ones have a low H _E as in population JD (0.011). The morphological divergence of leaf shape was estimated by the elliptical Fourier analysis on the data from 11 natural and four common garden populations. Leaf morphology analyses indicate the morphological divergence does not show strong correlation with the genetic differentiation ( R  = 0.260, P  = 0.069). By comparing the 95% confidence interval of Q _ST with that of F _ST, Q _ST values for five out of 12 quantitative traits are significantly higher than the average F _ST value over eight microsatellite loci. The comparison of F _ST and Q _ST suggests that two kinds of traits can be driven by different evolutionary forces, and the population divergence in leaf morphology is shaped by local selections.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 505–516.     

Contrasting levels of genetic diversity between the common, self-compatible Liparis kumokiri and rare, self-incompatible Liparis makinoana (Orchidaceae) in South Korea

Levels of allozyme variation and intrapopulation spatial genetic structure of the two terrestrial clonal orchids Liparis kumokiri , a self-compatible relatively common species, and L. makinoana , a self-incompatible rare species, were examined for 17 ( N  = 1875) and four ( N  = 425) populations, respectively, in South Korea. Populations of L. makinoana harboured high levels of genetic variation ( H _e = 0.319) across 15 loci. In contrast, L. kumokiri exhibited a complete lack of allozyme variation ( H _e = 0.000). Considering the lack of genetic variability, it is suggested that current populations of L. kumokiri in South Korea originated from a genetically depauperate ancestral population. For L. makinoana , a significant deficit of heterozygosity (mean F _IS = 0.198) was found in population samples excluding clonal ramets, suggesting that pollen dispersal is localized, generating biparental inbreeding. The significant fine-scale genetic structuring (≤ 2 m) found in a previous study, in addition to the moderate levels of population differentiation ( F _ST = 0.107) and the significant relationship between genetic and geographical distances ( r  = 0.680) found here, suggests a leptokurtic distribution of seed dispersal for L. makinoana . Although populations of L. makinoana harbour high levels of genetic variation, they are affected by a recent genetic bottleneck. This information suggests that genetic drift and limited gene flow could be the main evolutionary forces for speciation of a species-rich genus such as Liparis .  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 41–48.     

Genetic diversity and genetic structure of populations of Ranunculus japonicus Thunb. (Ranunculaceae)

Abstract In order to clarify the genetic diversity and population structure of Ranunculus japonicus , allozymic analysis was conducted on 60 populations in southwestern Japan. Considerable genetic variati ons were detected among the populations of R. japonicus . The genetic diversities within species ( H _es = 0.215) and within populations ( H _ep = 0.172) were slightly higher than those of other perennial herbs with widespread distribution and outcrossing plants. Significantly higher values of fixation index were detected in some populations, which might have arisen from restricted mating partners. The majority of genetic variation (approx. 80%) resided within a population and a moderate level of genetic differentiation ( G _ST = 0.203) was observed among populations. The F _ST value (0.203) suggests the existence of a substantial population structure in this species. The highly significant correlation between geographic distance and F _ST values indicates that isolation by distance has played an important role in the construction of the genetic structure of this species.     

Estimating contemporary early life-history dispersal in an estuarine fish: integrating molecular and otolith elemental approaches

Dispersal during the early life history of the anadromous rainbow smelt, Osmerus mordax , was examined using assignment testing and mixture analysis of multilocus genotypes and otolith elemental composition. Six spawning areas and associated estuarine nurseries were sampled throughout southeastern Newfoundland. Samples of adults and juveniles isolated by > 25 km displayed moderate genetic differentiation ( F _ST ~ 0.05), whereas nearby (< 25 km) spawning and nursery samples displayed low differentiation ( F _ST < 0.01). Self-assignment and mixture analysis of adult spawning samples supported the hypothesis of independence of isolated spawning locations (> 80% self-assignment) with nearby runs self-assigning at rates between 50 % and 70%. Assignment and mixture analysis of juveniles using adult baselines indicated high local recruitment at several locations (70–90%). Nearby (< 25 km) estuaries at the head of St Mary's Bay showed mixtures of individuals (i.e. 20–40% assignment to adjacent spawning location). Laser ablation inductively coupled mass spectrometry transects across otoliths of spawning adults of unknown dispersal history were used to estimate dispersal among estuaries across the first year of life. Single-element trends and multivariate discriminant function analysis (Sr:Ca and Ba:Ca) classified the majority of samples as estuarine suggesting limited movement between estuaries (< 0.5%). The mixtures of juveniles evident in the genetic data at nearby sites and a lack of evidence of straying in the otolith data support a hypothesis of selective mortality of immigrants. If indeed selective mortality of immigrants reduces the survivorship of dispersers, estimates of dispersal in marine environments that neglect survival may significantly overestimate gene flow.     

Comparison of quantitative and molecular genetic variation of native vs. invasive populations of purple loosestrife (Lythrum salicaria L., Lythraceae)

Study of adaptive evolutionary changes in populations of invasive species can be advanced through the joint application of quantitative and population genetic methods. Using purple loosestrife as a model system, we investigated the relative roles of natural selection, genetic drift and gene flow in the invasive process by contrasting phenotypical and neutral genetic differentiation among native European and invasive North American populations ( Q _ST −  F _ST analysis). Our results indicate that invasive and native populations harbour comparable levels of amplified fragment length polymorphism variation, a pattern consistent with multiple independent introductions from a diverse European gene pool. However, it was observed that the genetic variation reduced during subsequent invasion, perhaps by founder effects and genetic drift. Comparison of genetically based quantitative trait differentiation ( Q _ST) with its expectation under neutrality ( F _ST) revealed no evidence of disruptive selection ( Q _ST >  F _ST) or stabilizing selection ( Q _ST <  F _ST). One exception was found for only one trait (the number of stems) showing significant sign of stabilizing selection across all populations. This suggests that there are difficulties in distinguishing the effects of nonadaptive population processes and natural selection. Multiple introductions of purple loosestrife may have created a genetic mixture from diverse source populations and increased population genetic diversity, but its link to the adaptive differentiation of invasive North American populations needs further research.     

Microsatellite variation and population structure of the moor frog (Rana arvalis) in Scandinavia

Several recent studies have found amphibian populations to be genetically highly structured over rather short geographical distances, and that the rate of genetically effective dispersal may differ between the sexes. However, apart from the common frog ( Rana temporaria ) little is known about the genetic structuring and sex-biased dispersal in northern European amphibians. We investigated the patterns of genetic diversity and differentiation within and among Scandinavian populations of the moor frog ( Rana arvalis ) using microsatellite markers. The genetic diversity within local R. arvalis populations was not a simple linear negative function of latitude but a convex one: genetic diversity peaked in mid-latitude populations, and declined thereafter dramatically towards the north. The average degree of genetic differentiation among populations ( F _ST = 0.14) was lower than that observed for the common frog ( F _ST = 0.21), though the pattern of isolation by distance was similar for both species. Contrary to common frogs, no evidence for female-biased dispersal was found. The results reinforce the view that amphibian populations are—in general—highly structured over relatively small geographical distances, even in comparatively recently colonized areas.     

Male-biased dispersal in a tropical Australian snake (Stegonotus cucullatus, Colubridae)

Sex-based differences in dispersal distances can affect critical population parameters such as inbreeding rates and the spatial scale of local adaptation. Males tend to disperse further than females in mammals, whereas the reverse is true for birds; too few reptiles have been studied to reveal generalities for that group. Although reptiles are most diverse and abundant in the tropics, few tropical reptiles have been studied in this respect. We combine data from a long-term (10-year) mark–recapture study with genetic information (based on nine microsatellite markers) on slatey-grey snakes ( Stegonotus cucullatus , Colubridae) in the Australian wet-dry tropics. Males attain larger body sizes than females, and both genetic and mark–recapture data show that males also disperse further than females. Recapture records show that hatchling males dispersed away from their release points whereas hatchling females did not, and adult males moved further than adult females. In the genetic analysis, males contributed less to overall F _ST and relatedness than did females ( F _STm = 0.0025, F _STf = 0.0275, P  < 0.001; r _m = 0.0053; r _f = 0.0550; P  < 0.001). Spatial autocorrelation analyses within the largest population revealed a similar pattern, with spatial structuring stronger for females than males. Overall, our genetic analyses not only supported the mark–recapture data, but also extended our insights by revealing occasional long-distance dispersal not detected by the mark–recapture study.     

Genetic diversity and gene flow in collapsed and healthy abalone fisheries

Overexploitation of marine species invariably results in population decline but can also have indirect effects on ecological processes such as larval dispersal and recruitment that ultimately affect genetic diversity and population resilience. We compared microsatellite DNA variation among depleted and healthy populations of the black-lip abalone Haliotis rubra from Tasmania, Australia, to determine if over-fishing had affected genetic diversity. We also used genetic data to assess whether variation in the scale and frequency of larval dispersal was linked to greater population decline in some regions than in others, and if larval dispersal was sufficient to facilitate natural recovery of depleted populations. Surprisingly, allelic diversity was higher in depleted populations than in healthy populations ( P <  0.05). Significant subdivision across hundreds of metres among our sampling sites ( F _ST = 0.026, P  < 0.01), coupled with assignment tests, indicated that larval dispersal is restricted in all regions studied, and that abalone populations across Tasmania are largely self-recruiting. Low levels of larval exchange appear to occur at the meso-scale (7–20 km), but age estimates based on shell size indicated that successful migration of larvae between any two sites may happen only once every few years. We suggest that genetic diversity may be higher in depleted populations due to the higher relative ratio of migrant to self-recruiting larvae. In addition, we expect that recovery of depleted abalone populations will be reliant on sources of larvae at the meso-scale (tens of km), but that natural recovery is only likely to occur on a timescale unacceptable to fishers and resource managers.     

Population genetic structure in Myrtus communis L. in a chronically fragmented landscape in the Mediterranean: can gene flow counteract habitat perturbation?

Ancient managed landscapes provide ideal opportunities to assess the consequences of habitat fragmentation on the patterns of genetic diversity and gene flow in long-lived plant species. Using amplified fragment length polymorphism (AFLP) and allozyme markers, we quantified seed-mediated gene flow and population genetic diversity and structure in 14 populations of Myrtus communis (myrtle), a common endozoochorous shrub species of forest patches in lowland agricultural Mediterranean areas. Overall, allozyme diversity for myrtle was low (P₉₅   =   25%; A   =   1.411; H_e = 0.085) compared to other known populations, and a significant portion of populations (57%) had lower levels of allelic diversity and/or heterozygosity than expected at random, as shown by simulated resampling of the whole diversity of the landscape. We found significant correlations between allozyme variability and population size and patch isolation, but no significant inbreeding in any population. Genetic differentiation among populations for both allozyme and AFLP markers was significant (Φ_ST = 0.144 and Φ_ST = 0.142, respectively) but an isolation-by-distance pattern was not detected. Assignment tests on AFLP data indicated a high immigration rate in the populations ( ca. 20–22%), likely through effective seed dispersal across the landscape by birds and mammals. Our results suggest that genetic isolation is not the automatic outcome of habitat destruction since substantial levels of seed-mediated gene flow are currently detectable. However, even moderate rates of gene flow seem insufficient in this long-lived species to counteract the genetic erosion and differentiation imposed by chronic habitat destruction.     

Genetic structure and differentiation of Gentiana atuntsiensis W. W. Smith and G. striolata T. N. Ho (Gentianaceae) as revealed by ISSR markers

The Hengduan Mountains are the core region of the Himalaya hotspot, and are renowned for their high levels of endemism. Gentiana atuntsiensis and G. striolata are two closely related and morphologically similar species endemic to this region. In this study, inter-simple sequence repeat (ISSR) markers were used to investigate the genetic structure within these two species, as well as the differentiation between them. An analysis of molecular variance-derived estimate demonstrated only 13.5% of genetic differentiation between the two species. Considering their adjacent distribution patterns, low genetic divergence, and clear clustering into two groups, it is hypothesized that the two species arose from a rapid and recent speciation event induced mainly by geographical isolation. A relatively high level of genetic diversity was revealed in each species (Shannon's index of diversity: H _sp = 0.324 and 0.391; H _pop = 0.225 and 0.274; for G. atuntsiensis and G. striolata , respectively). Most of the genetic variation was partitioned within populations ( Ø _ST = 0.232 and 0.226 in G. atuntsiensis and G. striolata , respectively). The large population sizes, outcrossing breeding system, and small, light seeds that disperse widely may explain the genetic structure in both species.  © 2007 The Linnean Society of London. Botanical Journal of the Linnean Society , 2007, 154 , 225–232.     

Conservation genetics of Amorpha georgiana (Fabaceae), an endangered legume of the Southeastern United States

Amorpha georgiana (Fabaceae) is an endangered legume species found in longleaf pine savannas in the Southeastern United States. Approximately 900 individuals and 14 populations remain, most of which are concentrated in North Carolina. Eleven microsatellite loci were used to explore genetic diversity, population structure and recent population bottlenecks using genotypic data from 132 individuals collected at ten different localities. Although A. georgiana is quite rare, it exhibited high levels of genetic diversity (17.7 alleles/locus; H _o = 0.65, H _E = 0.75). Most of the genetic variation was found within rather than between populations of this species. The single remaining Georgia population was well differentiated from populations of the Carolinas ( F _ST > 0.1), which had weaker structure among them ( F _ST < 0.1). Only a geographically disjunct population showed strong evidence of a recent population bottleneck, perhaps due to a recent founder event. Hybridization with A. herbacea was also detected. For conservation management plans, A. georgiana populations in each geographic region (North Carolina, South Carolina and Georgia) plus a disjunct population in North Carolina (Holly Shelter) should be treated as separate management units for which in situ conservation, including habitat restoration and use of prescribed burns, should ensure persistence of this species and preservation of its evolutionary potential.     

Population genetic structure of the tiger prawn (Penaeus monodon) in the coastal waters of South China, based on mitochondrial DNA control region sequences

Genetic variation and population structure of Penaeus monodon in the coastal waters of South China were detected using mitochondrial DNA control region sequences. Eighty individuals were collected at Sanya, Shenzhen, Zhanjiang and Beihai; 69 haplotypes with 157 polymorphic sites were detected. Nucleotide diversity (π) of the combined samples (6.16 ± 3.01%) was much higher than many other species in Chinese seas, such as Penaeus japonicus , Portunus trituberculatus , and Acanthopagrus schlegeli . Genetic differentiation was significant between Beihai and Sanya (pairwise F _ST = 0.09836, P < 0.05), and between Beihai and Shenzhen (pairwise F _ST = 0.12153, P < 0.05). Significant genetic differentiation among all populations was found by analysis of molecular variance ( amova ) ( F _ST = 0.053, P = 0.037 < 0.05). The upgma dendrogram of the four populations showed Sanya and Shenzhen as the closest to each other, with Beihai having the greatest genetic distance from Sanya and Shenzhen. The tiger prawn of the coastal waters of South China should therefore be bred as two separated stocks, avoiding inbreeding or outbreeding selection of P. monodon in the captive breeding program. According to our results one source population is Beihai, and the others are from Sanya and Shenzhen.     

Contrasting genetic patterns and population histories in three threatened redfin species (Cyprinidae) from the Olifants River system, western South Africa

Differentiation occurred in different areas of the same river system in Pseudobarbus phlegethon and two sister species of the serrated redfin lineage ( Barbus calidus and Barbus erubescens ) of the Western Cape region of South Africa. In an analysis of 27 allozyme loci a deep divergence was found within P. phlegethon between the Olifants and Doring catchments (seven fixed allelic differences; 0·338 <  D  < 0·366; F _ST = 0·925). In contrast, speciation in the serrated redfin lineage occurred within the Doring catchment between B. calidus and B. erubescens (one fixed allelic difference; 0·008 <  D  < 0·052; F _ST = 0·760). Different niche preferences, behaviour and morphology probably played an important role in the formation of these contrasting patterns of genetic structure and suggest that B. calidus may have been better able to disperse between the Olifants and Doring catchments (no fixed allelic differences; 0 <  D  < 0·040; F _ST = 0·281) than P. phlegethon .     

Potential refugium on the Qinghai–Tibet Plateau revealed by the chloroplast DNA phylogeography of the alpine species Metagentiana striata (Gentianaceae)

Metagentiana striata is an alpine annual herbaceous plant endemic to the east of the Qinghai–Tibet (Q–T) Plateau and adjacent areas. The phylogeography of M. striata was studied by sequencing the chloroplast DNA (cpDNA) trn S– trn G intergenic spacer. Ten haplotypes were identified from an investigation of 232 individuals of M. striata from 14 populations covering the entire geographical range of this species. The level of differentiation amongst populations was very high ( G _ST = 0.746; N _ST = 0.774) and a significant phylogeographical structure was observed ( P  < 0.05). An analysis of molecular variance found a high variation amongst populations (76%), with F _ST = 0.762 (highly significant, P  < 0.001), indicating that little gene flow occurred amongst the different regions; this was explained by the isolation of populations by high mountains along the Q–T Plateau and adjacent areas ( N _m = 0.156). Only one ancestral haplotype (A) was common and widespread throughout the distributional range of M. striata. The populations of the Hengduan Mountains region of the south-eastern Q–T Plateau showed high diversity and uniqueness of haplotypes. It is suggested that this region was the potential refugium of M. striata during the Quaternary glaciation, and that interglacial and postglacial range expansion occurred from this refugium. This scenario was in good agreement with the results of nested clade analysis, which inferred that the current spatial distribution of cpDNA haplotypes and populations resulted from range expansion, together with past allopatric fragmentation events.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 125–140.     

Genetic population structure and dispersal in Atlantic Island caddisflies

SUMMARY 1. Population genetic structure of Wormaldia tagananana, a caddis with a narrow geographic range and endemic to the Canary Islands, was investigated by studying allozyme variation at 11 putative loci in five of the eight extant populations on Tenerife and La Gomera. Genetic variability, population structure and gene flow were compared with those reported previously in more widespread Trichoptera, particularly Canarian populations of the non-endemic limnephilid Mesophylax aspersus, to examine the hypothesis that the Wormaldia , with its restricted range, would exhibit relatively little genetic variability and gene flow.
2. Despite it being a narrow-range island endemic, genetic variability in populations of W. tagananana is broadly similar to values reported for more widespread caddis.
3. Significant genetic population structure was observed in W. tagananana (overall F _ST = 0.387), greater than that seen in M. aspersus and amongst the highest reported for lotic caddis to date. Several site- and island-specific alleles were reported, providing further evidence for the relative isolation of individual Wormaldia populations.
4. Significant deviations from Hardy–Weinberg equilibrium were found in four of five populations (overall F _IS = 0.675). This could result from within-locality population substructuring, or offspring within a reach being the product of a limited number of matings.
5. This genetic evidence supports the hypothesis that the restricted range of W. tagananana is, at least in part, because of limited dispersal ability.     

Phylogeographic structure of Pinus strobiformis Engelm. across the Chihuahuan Desert filter-barrier

Aim  To explore the genetic and phylogeographic structure of a temperate forest species, Pinus strobiformis Englem., in a subtropical region in the context of climate change during the Pleistocene. It is expected that the colder conditions during glacial stages favoured range expansions of P. strobiformis , thus promoting gene flow.
Location  Mexico and the United States.
Methods  Estimates of genetic diversity and structure were obtained using chloroplast microsatellite loci of 23 populations of P. strobiformis across its entire range, seven neighbouring populations of Pinus ayacahuite Ehrenb. ex. Schtdl, and one population of Pinus flexilis James.
Results  The genetic diversity of P. strobiformis ( H _e = 0.856) was found to be high, especially in western populations, whereas eastern populations were less variable and more genetically similar to P. ayacahuite of central Mexico. We found evidence of significant phylogeographic structure ( N _ST = 0.444; P  =   0.026), high genetic structure ( R _ST = 0.270), and isolation by distance. Pairwise R _ST and samova (spatial analysis of molecular variance) results indicated an east–west partition of genetic variation, with populations within each group showing little differentiation and no isolation by distance.
Main conclusions  The phylogeographic structure of P. strobiformis across the entire range was pronounced, with two main genetic and geographic groups separated by the Chihuahuan Desert. However, within each of the two groups there was little population differentiation and no isolation by distance, suggesting genetic connectivity as a result of population expansions within these areas during glacial stages.     

Genetics of the peripheral populations of the alpine bullhead, Cottus poecilopus (Scorpaeniformes, Cottidae) in Poland

The alpine bullhead ( Cottus poecilopus ) in Poland is highly polymorphic ( P for examined populations in the range of 0.0–0.45, mean P  = 0.11, P for species 0.64) in seven out of 11 loci studied ( Pgd-1, Mdh-1, Ck-1, Gpd-1, Gpd-2, Gpi-1, Gpi-2 ). However, they reveal very low heterozygosity (mean H _o = 0.007, mean H _e = 0.019), which may result from population subdivisions, small genetically effective size ( N _e) of some populations and frequent inbreeding, the latter being probably mediated through polygyny. The index of genetic differentiation ( G _ST) for the Polish metapopulation equals 0.48, which is relatively high. By far, the strongest are genetic differences between the Sudeten-Carpathian group and the Hańcza population. Gene flow between the Sudeten-Carpathian group and the Hańcza population is very limited and their divergence may have started as early as the last (Eemian) interglacial period.