Population structure and genetic variation in the endangered Giant Kangaroo Rat (<Emphasis Type="Italic">Dipodomys ingens</Emphasis>)

Populations of the endangered giant kangaroo rat, Dipodomys ingens (Heteromyidae), have suffered increasing fragmentation and isolation over the recent past, and the distribution of this unique rodent has become restricted to 3% of its historical range. Such changes in population structure can significantly affect effective population size and dispersal, and ultimately increase the risk of extinction for endangered species. To assess the fine-scale population structure, gene flow, and genetic diversity of remnant populations of Dipodomys ingens, we examined variation at six microsatellite DNA loci in 95 animals from six populations. Genetic subdivision was significant for both the northern and southern part of the kangaroo rat’s range although there was considerable gene flow among southern populations. While regional gene diversity was relatively high for this endangered species, hierarchical F-statistics of northern populations in Fresno and San Benito counties suggested non-random mating and genetic drift within subpopulations. We conclude that effective dispersal, and therefore genetic distances between populations, is better predicted by ecological conditions and topography of the environment than linear geographic distance between populations. Our results are consistent with and complimentary to previous findings based on mtDNA variation of giant kangaroo rats. We suggest that management plans for this endangered rodent focus on protection of suitable habitat, maintenance of connectivity, and enhancement of effective dispersal between populations either through suitable dispersal corridors or translocations.     

Phylogenetic relationships, evolutionary origin, taxonomic status, and genetic structure of the endangered local Lower Elbe river (Germany) endemic Oenanthe conioides (Nolte ex Rchb.f.) Lange (Apiaceae): ITS and AFLP evidence

Oenanthe conioides is an endangered local endemic of the Lower Elbe river region in Germany where it is found in areas with freshwater tides. Internal transcribed spacer (ITS) and amplified fragment length polymorphism (AFLP) markers were used to investigate its phylogenetic relationships, evolutionary origin, taxonomic status, and genetic structure.Oe. conioides is most closely related to Oe. aquatica and Oe. fluviatilis, and cannot be distinguished from Oe. aquatica by ITS sequence variation. Oe. aquatica is found mainly in standing or slow-flowing freshwater habitats. The AFLP analysis indicated that Oe. conioides may constitute a monophyletic lineage nested within Oe. aquatica. Considering this result on the background of the sympatric distribution of the two species and their ecological differentiation, it is hypothesized that Oe. conioides arose sympatrically from Oe. aquatica through ecological divergence. It is concluded that Oe. conioides is best considered a subspecies of Oe. aquatica.AFLP analysis of Oe. conioides revealed low levels of genetic differentiation among populations reflecting the small geographical distance, the recent decline in population number and size, the connection of populations through the river, and their presumably high population dynamics.Considering this pattern of genetic variation, it is concluded that no individual population can be singled out as being particularly important from a genetic point of view. Also, all populations could be used as source material should the establishment of new populations or the enlargement of small populations be considered as a measure to consolidate the persistence of the species.     

Combining genetic and ecological data to assess the conservation status of the endangered Ethiopian walia ibex

Knowledge about the phylogenetic history, genetic variation and ecological requirements of a species is important for its conservation and management. Unfortunately, for many species this information is lacking. Here we use multiple approaches (phylogenetics, population genetics and ecological modelling) to evaluate the evolutionary history and conservation status of Capra walie , an endangered flagship species of wild goat endemic to Ethiopia. The analysis of mitochondrial cytochrome b and Y-chromosome DNA sequences suggests that C. walie forms a monophyletic clade with Capra nubiana , but potentially has been isolated for up to 0.8 million years from this closely related species. Microsatellite DNA analyses show that C. walie has very low genetic variation (mean heterozygosity=0.35) compared with other endangered mammals. This reduced variation likely derives from a prolonged demographic decline and small effective population size. Ecological niche modelling using the bioclimatic features of habitats occupied by C. walie , suggests ecological differences between C. walie and C. nubiana , and identifies the areas most suitable for future reintroductions of C. walie . The genetic and bioclimatic data suggest that C. walie is distinct and requires immediate conservation actions including genetic monitoring and reintroductions to establish independent populations. This study illustrates how combining noninvasive sampling along with genetic and ecological (bioclimatic) approaches can help assess conservation status of poorly known species.     

AN ADAPTIVE RADIATION OF FROGS IN A SOUTHEAST ASIAN ISLAND ARCHIPELAGO

Living amphibians exhibit a diversity of ecologies, life histories, and species‐rich lineages that offers opportunities for studies of adaptive radiation. We characterize a diverse clade of frogs (Kaloula, Microhylidae) in the Philippine island archipelago as an example of an adaptive radiation into three primary habitat specialists or ecotypes. We use a novel phylogenetic estimate for this clade to evaluate the tempo of lineage accumulation and morphological diversification. Because species‐level phylogenetic estimates for Philippine Kaloula are lacking, we employ dense population sampling to determine the appropriate evolutionary lineages for diversification analyses. We explicitly take phylogenetic uncertainty into account when calculating diversification and disparification statistics and fitting models of diversification. Following dispersal to the Philippines from Southeast Asia, Kaloula radiated rapidly into several well‐supported clades. Morphological variation within Kaloula is partly explained by ecotype and accumulated at high levels during this radiation, including within ecotypes. We pinpoint an axis of morphospace related directly to climbing and digging behaviors and find patterns of phenotypic evolution suggestive of ecological opportunity with partitioning into distinct habitat specialists. We conclude by discussing the components of phenotypic diversity that are likely important in amphibian adaptive radiations.     

Rangewide phylogeography and landscape genetics of the Western U.S. endemic frog Rana boylii (Ranidae): implications for the conservation of frogs and rivers

Genetic data are increasingly being used in conservation planning for declining species. We sampled both the ecological and distributional limits of the foothill yellow-legged frog, Rana boylii to characterize mitochondrial DNA (mtDNA) variation in this declining, riverine amphibian. We evaluated 1525 base pairs (bp) of cytochrome b and ND2 fragments for 77 individuals from 34 localities using phylogenetic and population genetic analyses. We constructed gene trees using maximum likelihood and Bayesian inference, and quantified genetic variance (using AMOVA and partial Mantel tests) within and among hydrologic regions and river basins. Several moderately supported, geographically-cohesive mtDNA clades were recovered for R. boylii. While genetic variation was low among populations in the largest, most inclusive clade, samples from localities at the edges of the geographic range demonstrated substantial genetic divergence from each other and from more central populations. Hydrologic regions and river basins, which represent likely dispersal corridors for R. boylii, accounted for significant levels of genetic variation. These results suggest that both rivers and larger hydrologic and geographic regions should be used in conservation planning for R. boylii.     

Lineage diversification and historical demography of a sky island salamander,Plethodon ouachitae,from the Interior Highlands

Sky islands provide ideal opportunities for understanding how climatic changes associated with Pleistocene glacial cycles influenced species distributions, genetic diversification, and demography. The salamander Plethodon ouachitae is largely restricted to high‐elevation, mesic forest on six major mountains in the Ouachita Mountains. Because these mountains are separated by more xeric, low‐elevation valleys, the salamanders appear to be isolated on sky islands where gene flow among populations on different mountains may be restricted. We used DNA sequence data along with ecological niche modelling and coalescent simulations to test several hypotheses related to diversifications in sky island habitats. Our results revealed that P. ouachitae is composed of seven well‐supported lineages structured across six major mountains. The species originated during the Late Pliocene, and lineage diversification occurred during the Middle Pleistocene in a stepping stone fashion with a cyclical pattern of dispersal to a new mountain followed by isolation and divergence. Diversification occurred primarily on an east–west axis, which is likely related to the east–west orientation of the Ouachita Mountains and the more favourable cooler and wetter environmental conditions on north slopes compared to south‐facing slopes and valleys. All non‐genealogical coalescent methods failed to detect significant population expansion in any lineages. Bayesian skyline plots showed relatively stable population sizes over time, but indicated a slight to moderate amount of population growth in all lineages starting approximately 10 000–12 000 years ago. Our results provide new insight into sky island diversifications from a previously unstudied region, and further demonstrate that climatic changes during the Pleistocene had profound effects on lineage diversification and demography, especially in species from environmentally sensitive habitats in montane regions.     

Reduced MHC class II diversity in island compared to mainland populations of the black-footed rock-wallaby (<Emphasis Type="Italic">Petrogale lateralis lateralis</Emphasis>)

Many animal populations that are endangered in mainland areas exist in stable island populations, which have the potential to act as an “ark” in case of mainland population declines. Previous studies have found neutral genetic variation in such species to be up to an order of magnitude lower in island compared to mainland populations. If low genetic variation is prevalent across fitness-related loci, this would reduce the effectiveness of island populations as a source of individuals to supplement declining mainland populations or re-establish extinct mainland populations. One such species, the black-footed rock-wallaby (Petrogale lateralis lateralis), exists within fragmented mainland populations and small island populations off Western Australia. We examined sequence variation in this species within a fitness-related locus under positive selection, the MHC class II DAB β1 locus. The mainland populations displayed greater levels of allelic diversity (4–7 alleles) than the island population, despite being small and isolated, and contained at least two DAB gene copies. The island population displayed low allelic diversity (2 alleles) and fewer alleles per individual in comparison to mainland populations, and probably possesses only one DAB gene copy. The patterns of DAB diversity suggested that the island population has a markedly lower level of genetic variation than the mainland populations, in concordance with results from microsatellites (genotyped in a previous study), but preserved unique alleles which were not found in mainland populations. Where possible, conservation actions should pool individuals from multiple populations, not only island populations, for translocation programs, and focus on preventing further declines in mainland populations.     

Contrasting demographic and genetic estimates of dispersal in the endangered Coahuilan box turtle: a contemporary approach to conservation

The evolutionary viability of an endangered species depends upon gene flow among subpopulations and the degree of habitat patch connectivity. Contrasting population connectivity over ecological and evolutionary timescales may provide novel insight into what maintains genetic diversity within threatened species. We employed this integrative approach to evaluating dispersal in the critically endangered Coahuilan box turtle (Terrapene coahuila) that inhabits isolated wetlands in the desert‐spring ecosystem of Cuatro Ciénegas, Mexico. Recent wetland habitat loss has altered the spatial distribution and connectivity of habitat patches; and we therefore predicted that T. coahuila would exhibit limited movement relative to estimates of historic gene flow. To evaluate contemporary dispersal patterns, we employed mark–recapture techniques at both local (wetland complex) and regional (intercomplex) spatial scales. Gene flow estimates were obtained by surveying genetic variation at nine microsatellite loci in seven subpopulations located across the species’ geographical range. The mark–recapture results at the local spatial scale reveal frequent movement among wetlands that was unaffected by interwetland distance. At the regional spatial scale, dispersal events were relatively less frequent between wetland complexes. The complementary analysis of population genetic substructure indicates strong historic gene flow (global F_ST = 0.01). However, a relationship of genetic isolation by distance across the geographical range suggests that dispersal limitation exists at the regional scale. Our approach of contrasting direct and indirect estimates of dispersal at multiple spatial scales in T. coahuila conveys a sustainable evolutionary trajectory of the species pending preservation of threatened wetland habitats and a range‐wide network of corridors.     

MACRO- AND MICROGEOGRAPHIC STRUCTURE OF A SPATIALLY SUBDIVIDED BEETLE SPECIES IN NATURE

Spatial subdivision of species can affect their population structure by allowing processes such as limited dispersal, spatial heterogeneity in selective pressures, small population sizes, and random events to operate. By studying species restricted to islands or “island” habitats, one can attempt to determine which of these factors have affected the current structure of the population. Collops georgianus (Coleoptera: Melyridae), a beetle species endemic to the “island” habitat of granitic rock outcrops, was chosen to see how its spatially subdivided distribution has affected its genetic structure. Its genetic structure was examined on both a macrogeographic and a microgeographic level using protein electrophoresis. Macrogeographically, 12 populations throughout its range were sampled. The discontinuous distribution of outcrops, and thus populations, throughout its range, has determined the connectivity of the populations. Significant variation in allele frequencies and substructuring (F_ST = 0.192) was found throughout the range, but there was no spatial autocorrelation. Microgeographically, in the central part of the range, where outcrops are denser and more continuously distributed in space, there was evidence of isolation by distance. Very little variation in allele frequencies was found, but a low but significant level of substructuring occurred among the populations. Comparison of disjunct and continuous populations microgeographically revealed no effect of disjunct distributions, although a significant effect of distance was detected. Effective population size variation among populations and between years, compounded with the effects of local extinctions, suggest that random processes such as drift and founder effects are important determinants of the population's genetic structure.     

Low genetic diversity and local adaptive divergence of Dracaena cambodiana (Liliaceae) populations associated with historical population bottlenecks and natural selection: an endangered long‐lived tree endemic to Hainan Island,China

Historical population bottlenecks and natural selection have important effects on the current genetic diversity and structure of long‐lived trees. Dracaena cambodiana is an endangered, long‐lived tree endemic to Hainan Island, China. Our field investigations showed that only 10 populations remain on Hainan Island and that almost all have been seriously isolated and grow in distinct habitats. A considerable amount of genetic variation at the species level, but little variation at the population level, and a high level of genetic differentiation among the populations with limited gene flow in D. cambodiana were detected using inter‐simple sequence repeat (ISSR) and random amplified polymorphic DNA (RAPD) analyses. No significant correlation was found between genetic diversity and actual population size, as the genetic diversities were similar regardless of population size. The Mantel test revealed that there was no correlation between genetic and geographic distances among the 10 populations. The UPGMA, PCoA and Bayesian analyses showed that local adaptive divergence has occurred among the D. cambodiana populations, which was further supported by habitat‐private fragments. We suggest that the current genetic diversity and population differentiation of D. cambodiana resulted from historical population bottlenecks and natural selection followed by historical isolation. However, the lack of natural regeneration of D. cambodiana indicates that former local adaptations with low genetic diversity may have been genetically weak and are unable to adapt to the current ecological environments.     

The impact of pollination syndrome and habitat on gene flow: a comparative study of two Streptocarpus (Gesneriaceae) species

Gene flow through pollen and seed dispersal is important in terms of population differentiation and eventually speciation. Seed and pollen flow are affected in turn by habitats and pollen vectors. We examined the effect of different pollinators and habitats on gene flow by comparing two species of Streptocarpus, using microsatellite and chloroplast RFLP markers. Populations of the forest-dwelling S. primulifolius were highly differentiated according to nuclear microsatellite data and had mutually exclusive chloroplast haplotypes. This result is congruent with infrequent seed dispersal and limited between-population foraging by the long-tongued fly pollinator Stenobasipteron wiedemanni. In contrast, populations of S. dunnii growing in exposed crags had lower levels of population differentiation according to both nuclear and chloroplast data, congruent with a hypothesis of more effective between population seed dispersal and greater pollen-mediated gene flow due to the sunbird pollinator Nectarinia famosa. The population genetic behavior of these species is reflected in their taxonomy and phylogenetic position; S. primulifolius belongs to a taxonomically complex clade in which recent speciation is evident, while the clade containing S. dunnii is characterized by taxonomically well-defined species on longer phylogenetic branches. Our study shows that pollinator movements and seed dispersal patterns are a major determinant of the evolutionary trajectories of these species.     

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.     

ISSR Analysis of the Genetic Diversity of the Endangered Species Sinopodophyllum hexandrum （Royle） Ying from Western Sichuan Province, China

Slnopodophyllum hexandrum （Royle） Ying Is an Important medicinal and endangered species. Inter-simple sequence repeats （ISSR） analysis was conducted on seven natural populations from western Slchuan Province to Investigate the genetic diversity of S. hexandrum. Leaf samples of 140 Individuals were collected. Of the 139 discernible fragments generated by 12 selected primers （among 100 primers）, 54 appeared to be polymorphlc. The percentage of polymorphlc bands （PPB） was 38.85% at the species level, and PPB within a population ranged from 7.91% to 23.74%. Low levels of genetic variation （He = 0.092, Ho = 0.142） and high levels of genetic differentiation among the populations （Gst= 62.25%） was detected on the basis of results from POPGENE and analysis of molecular variance （AMOVA）, respectively. Furthermore, the limited gene flow （Nm = 0.361） may result from biological characteristics, such as self-pollination and short distance seed dispersal. Based on the genetic and ecological Information available for S. hexandrum, we propose some appropriate strategies for the conservation of the endangered medicinal species in this region, namely rescuing and conserving the core populations for in situ conservation and sampling and preserving more populations with fewer Individuals from each population for ex situ conservation.     

Variability of Wing Size and Shape in Three Populations of a Recent Brazilian Invader, Zaprionus indianus (Diptera: Drosophilidae), from Different Habitats

Zaprionus indianus (Diptera: Drosophilidae) is an African species that was introduced in Brazil near the end of the 1990’s decade. To evaluate the adaptive potential of morphological traits in natural populations of this recently introduced species, we have investigated wing size and shape variation at Rio de Janeiro populations only two years after the first record of Z. indianus in Brazil. Significant genetic differences among populations from three distinct ecological habitats were detected. The heritability and evolvability estimates show that, even with the population bottleneck that should have occurred during the invasion event, an appreciable amount of additive genetic variation for wing size and shape was retained. Our results also indicated a greater influence of environmental variation on wing size than on wing shape. The importance of quantitative genetic variability and plasticity in the successful establishment and dispersal of Z. indianus in the Brazilian territory is then discussed.     

Genetic structure among Charadrius plovers on the African mainland and islands of Madagascar and St Helena

Colonization of islands by long-distance dispersers has great impact on genetic diversification among populations and may spearhead speciation events. We investigated intra- and interspecific divergence in Charadrius plovers with populations on mainland Africa, Madagascar and St Helena. We analysed microsatellite loci and sequence data from four nuclear and two mitochondrial gene regions. Charadrius plovers are shorebirds with high dispersal and mobility. Our results confirmed genetic differentiation between Madagascar and mainland populations of three plover species (White-fronted Plover Charadrius marginatus, Kittlitz's Plover Charadrius pecuarius and, based on sequence data only, Three-banded Plover Charadrius tricollaris) but highlight substantial variation in levels of intraspecific divergence among the three species. Namely, the Kittlitz's Plover, a dispersive habitat generalist with a polygamous mating system, exhibited lower island–mainland differentiation (0.05% COI sequence divergence) compared with the two monogamous species, the White-fronted Plover (0.6% COI divergence) and Three-banded Plover (1.6% COI divergence). In addition, past colonization of the islands of St Helena and Madagascar by ancestors of today's Kittlitz's Plover has led to the evolution of two endemic island species, the Madagascar Plover Charadrius thoracicus and the more closely-related St Helena Plover Charadrius sanctaehelenae. We discuss the factors driving species differences in island–mainland divergence and highlight the importance of conserving genetically unique island populations and island habitats to safeguard future evolutionary potential.     

Spatial and ecological population genetic structures within two island‐endemic Aeonium species of different niche width

The Crassulacean genus Aeonium is a well‐known example for plant species radiation on oceanic archipelagos. However, while allopatric speciation among islands is documented for this genus, the role of intra‐island speciation due to population divergence by topographical isolation or ecological heterogeneity has not yet been addressed. The aim of this study was to investigate intraspecific genetic structures and to identify spatial and ecological drivers of genetic population differentiation on the island scale. We analyzed inter simple sequence repeat variation within two island‐endemic Aeonium species of La Palma: one widespread generalist that covers a large variety of different habitat types (Ae. davidbramwellii) and one narrow ecological specialist (Ae. nobile), in order to assess evolutionary potentials on this island. Gene pool differentiation and genetic diversity patterns were associated with major landscape structures in both species, with phylogeographic implications. However, overall levels of genetic differentiation were low. For the generalist species, outlier loci detection and loci–environment correlation approaches indicated moderate signatures of divergent selection pressures linked to temperature and precipitation variables, while the specialist species missed such patterns. Our data point to incipient differentiation among populations, emphasizing that ecological heterogeneity and topographical structuring within the small scales of an island can foster evolutionary processes. Very likely, such processes have contributed to the radiation of Aeonium on the Canary Islands. There is also support for different evolutionary mechanisms between generalist and specialist species.     

Contrasting genetic responses to population fragmentation in a coevolving fig and fig wasp across a mainland–island archipelago

Interacting species of pollinator–host systems, especially the obligate ones, are sensitive to habitat fragmentation, due to the nature of mutual dependence. Comparative studies of genetic structure can provide insights into how habitat fragmentation contributes to patterns of genetic divergence among populations of the interacting species. In this study, we used microsatellites to analyse genetic variation in Chinese populations of a typical mutualistic system – Ficus pumila and its obligate pollinator Wiebesia sp. 1 – in a naturally fragmented landscape. The plants and wasps showed discordant patterns of genetic variation and geographical divergence. There was no significant positive relationship in genetic diversity between the two species. Significant isolation‐by‐distance (IBD) patterns occurred across the populations of F. pumila and Wiebesia sp. 1 as whole, and IBD also occurred among island populations of the wasps, but not the plants. However, there was no significant positive relationship in genetic differentiation between them. The pollinator populations had significantly lower genetic variation in small habitat patches than in larger patches, and three island pollinator populations showed evidence of a recent bottleneck event. No effects of patch size or genetic bottlenecks were evident in the plant populations. Collectively, the results indicate that, in more fragmented habitats, the pollinators, but not the plants, have experienced reduced genetic variation. The contrasting patterns have multiple potential causes, including differences in longevity and hence number of generations experiencing fragmentation; different dispersal patterns, with the host's genes dispersed as seeds as well as a result of pollen dispersal via the pollinator; asymmetrical responses to fluctuations in partner populations; and co‐existence of a rare second pollinating wasp on some islands. These results indicate that strongly interdependent species may respond in markedly different ways to habitat fragmentation.     

TESTING THE LINK BETWEEN POPULATION GENETIC DIFFERENTIATION AND CLADE DIVERSIFICATION IN COSTA RICAN ORCHIDS

Species population genetics could be an important factor explaining variation in clade species richness. Here, we use newly generated amplified fragment length polymorphism (AFLP) data to test whether five pairs of sister clades of Costa Rican orchids that differ greatly in species richness also differ in average neutral genetic differentiation within species, expecting that if the strength of processes promoting differentiation within species is phylogenetically heritable, then clades with greater genetic differentiation should diversify more. Contrary to expectation, neutral genetic differentiation does not correlate directly with total diversification in the clades studied. Neutral genetic differentiation varies greatly among species and shows no heritability within clades. Half of the variation in neutral genetic differentiation among populations can be explained by ecological variables, and species‐level traits explain the most variation. Unexpectedly, we find no isolation by distance in any species, but genetic differentiation is greater between populations occupying different niches. This pattern corresponds with those observed for microscopic eukaryotes and could reflect effective widespread dispersal of tiny and numerous orchid seeds. Although not providing a definitive answer to whether population genetics processes affect clade diversification, this work highlights the potential for addressing new macroevolutionary questions using a comparative population genetic approach.     

Population genetics of the carinate pillsnail, <Emphasis Type="Italic">Euchemotrema hubrichti</Emphasis>: genetic structure on a small spatial scale

Euchemotrema hubrichti (Pilsbry HA (1940) Volume 1, Part 2. Monographs of the Academy of Natural Sciences, Philadelphia, 3, I-VI, 2, 575–994, I-IX) is a polygyrid land snail known only from the Larue Pine Hills region of southwestern Illinois, USA. Despite the restricted range of the species, observations in the field suggested that patterns of genetic variation within E. hubrichti might show geographic structure. To assess the dispersal potential of E. hubrichti, a mark-recapture experiment was performed at two sites <100 meters apart. To evaluate the geographic distribution of genetic variation, a region of the mitochondrial cytochrome c oxidase subunit I gene was sequenced from 53 snails collected from sites spanning the species range. Mark-recapture experiments suggested that population sizes at two sites were low and migration between sites was not detected. AMOVA and nested clade analysis (NCA) revealed significant genetic structure among sites. Two sites in particular appeared to be isolated from the others based on nested clade analysis. AMOVA also detected significant genetic differentiation among sites, but partitioning the data into two groups (populations 1 and 2) based on the NCA results did not explain a significant amount of genetic variation. Coalescent methods suggested that population sizes and migration rates for populations 1 and 2 are unequal. These patterns are likely due to the low dispersal ability of E. hubrichti and patchiness of preferred E. hubrichti habitat rather than an ancient vicariant event. These preliminary findings have implications both for the conservation of this species and for the population genetics of any spatially restricted endemic species with low dispersal ability.     

Intact landscape promotes gene flow and low genetic structuring in the threatened Eastern Massasauga Rattlesnake

Genetic structuring of wild populations is dependent on environmental, ecological, and life‐history factors. The specific role environmental context plays in genetic structuring is important to conservation practitioners working with rare species across areas with varying degrees of fragmentation. We investigated fine‐scale genetic patterns of the federally threatened Eastern Massasauga Rattlesnake (Sistrurus catenatus) on a relatively undisturbed island in northern Michigan, USA. This species often persists in habitat islands throughout much of its distribution due to extensive habitat loss and distance‐limited dispersal. We found that the entire island population exhibited weak genetic structuring with spatially segregated variation in effective migration and genetic diversity. The low level of genetic structuring contrasts with previous studies in the southern part of the species’ range at comparable fine scales (~7 km), in which much higher levels of structuring were documented. The island population''s genetic structuring more closely resembles that of populations from Ontario, Canada, that occupy similarly intact habitats. Intrapopulation variation in effective migration and genetic diversity likely corresponds to the presence of large inland lakes acting as barriers and more human activity in the southern portion of the island. The observed genetic structuring in this intact landscape suggests that the Eastern Massasauga is capable of sufficient interpatch movements to reduce overall genetic structuring and colonize new habitats. Landscape mosaics with multiple habitat patches and localized barriers (e.g., large water bodies or roads) will promote gene flow and natural colonization for this declining species.