Anthropogenic Habitats Facilitate Dispersal of an Early Successional Obligate: Implications for Restoration of an Endangered Ecosystem

Landscape modification and habitat fragmentation disrupt the connectivity of natural landscapes, with major consequences for biodiversity. Species that require patchily distributed habitats, such as those that specialize on early successional ecosystems, must disperse through a landscape matrix with unsuitable habitat types. We evaluated landscape effects on dispersal of an early successional obligate, the New England cottontail (Sylvilagus transitionalis). Using a landscape genetics approach, we identified barriers and facilitators of gene flow and connectivity corridors for a population of cottontails in the northeastern United States. We modeled dispersal in relation to landscape structure and composition and tested hypotheses about the influence of habitat fragmentation on gene flow. Anthropogenic and natural shrubland habitats facilitated gene flow, while the remainder of the matrix, particularly development and forest, impeded gene flow. The relative influence of matrix habitats differed between study areas in relation to a fragmentation gradient. Barrier features had higher explanatory power in the more fragmented site, while facilitating features were important in the less fragmented site. Landscape models that included a simultaneous barrier and facilitating effect of roads had higher explanatory power than models that considered either effect separately, supporting the hypothesis that roads act as both barriers and facilitators at all spatial scales. The inclusion of LiDAR-identified shrubland habitat improved the fit of our facilitator models. Corridor analyses using circuit and least cost path approaches revealed the importance of anthropogenic, linear features for restoring connectivity between the study areas. In fragmented landscapes, human-modified habitats may enhance functional connectivity by providing suitable dispersal conduits for early successional specialists.     

Genetic costructure in a meta‐community under threat of habitat fragmentation

Habitat fragmentation increasingly threatens the services provided by natural communities and ecosystem worldwide. An understanding of the eco‐evolutionary processes underlying fragmentation‐compromised communities in natural settings is lacking, yet critical to realistic and sustainable conservation. Through integrating the multivariate genetic, biotic and abiotic facets of a natural community module experiencing various degrees of habitat fragmentation, we provide unique insights into the processes underlying community functioning in real, natural conditions. The focal community module comprises a parasitic butterfly of conservation concern and its two obligatory host species, a plant and an ant. We show that both historical dispersal and ongoing habitat fragmentation shape population genetic diversity of the butterfly Phengaris alcon and its most limited host species (the plant Gentiana pneumonanthe). Genetic structure of each species was strongly driven by geographical structure, altitude and landscape connectivity. Strikingly, however, was the strong degree of genetic costructure among the three species that could not be explained by the spatial variables under study. This finding suggests that factors other than spatial configuration, including co‐evolutionary dynamics and shared dispersal pathways, cause parallel genetic structure among interacting species. While the exact contribution of co‐evolution and shared dispersal routes on the genetic variation within and among communities deserves further attention, our findings demonstrate a considerable degree of genetic parallelism in natural meta‐communities. The significant effect of landscape connectivity on the genetic diversity and structure of the butterfly also suggests that habitat fragmentation may threaten the functioning of the community module on the long run.     

Spatial genetic analysis of two polyploid macrophytes reveals high connectivity in a modified wetland

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Landscape genetics reveals unique and shared effects of urbanization for two sympatric pool‐breeding amphibians

Metapopulation‐structured species can be negatively affected when landscape fragmentation impairs connectivity. We investigated the effects of urbanization on genetic diversity and gene flow for two sympatric amphibian species, spotted salamanders (Ambystoma maculatum) and wood frogs (Lithobates sylvaticus), across a large (>35,000 km²) landscape in Maine, USA, containing numerous natural and anthropogenic gradients. Isolation‐by‐distance (IBD) patterns differed between the species. Spotted salamanders showed a linear and relatively high variance relationship between genetic and geographic distances (r = .057, p < .001), whereas wood frogs exhibited a strongly nonlinear and lower variance relationship (r = 0.429, p < .001). Scale dependence analysis of IBD found gene flow has its most predictable influence (strongest IBD correlations) at distances up to 9 km for spotted salamanders and up to 6 km for wood frogs. Estimated effective migration surfaces revealed contrasting patterns of high and low genetic diversity and gene flow between the two species. Population isolation, quantified as the mean IBD residuals for each population, was associated with local urbanization and less genetic diversity in both species. The influence of geographic proximity and urbanization on population connectivity was further supported by distance‐based redundancy analysis and multiple matrix regression with randomization. Resistance surface modeling found interpopulation connectivity to be influenced by developed land cover, light roads, interstates, and topography for both species, plus secondary roads and rivers for wood frogs. Our results highlight the influence of anthropogenic landscape features within the context of natural features and broad spatial genetic patterns, in turn supporting the premise that while urbanization significantly restricts interpopulation connectivity for wood frogs and spotted salamanders, specific landscape elements have unique effects on these two sympatric species.     

Landscape genetics of the Alpine newt (<Emphasis Type="Italic">Mesotriton alpestris</Emphasis>) inferred from a strip-based approach

Habitat destruction and fragmentation are known to strongly affect dispersal by altering the quality of the environment between populations. As a consequence, lower landscape connectivity is expected to enhance extinction risks through a decrease in gene flow and the resulting negative effects of genetic drift, accumulation of deleterious mutations and inbreeding depression. Such phenomena are particularly harmful for amphibian species, characterized by disjunct breeding habitats. The dispersal behaviour of amphibians being poorly understood, it is crucial to develop new tools, allowing us to determine the influence of landscape connectivity on the persistence of populations. In this study, we developed a new landscape genetics approach that aims at identifying land-uses affecting genetic differentiation, without a priori assumptions about associated ecological costs. We surveyed genetic variation at seven microsatellite loci for 19 Alpine newt (Mesotriton alpestris) populations in western Switzerland. Using strips of varying widths that define a dispersal corridor between pairs of populations, we were able to identify land-uses that act as dispersal barriers (i.e. urban areas) and corridors (i.e. forests). Our results suggest that habitat destruction and landscape fragmentation might in the near future affect common species such as M. alpestris. In addition, by identifying relevant landscape variables influencing population structure without unrealistic assumptions about dispersal, our method offers a simple and flexible tool of investigation as an alternative to least-cost models and other approaches.     

Dispersal via stream corridors structures populations of the endangered St. Francis’ satyr butterfly (Neonympha mitchellii francisci)

Habitat fragmentation may reduce gene flow and population viability of rare species. We tested whether riparian corridors enhanced gene flow and if human habitat modification between riparian corridors subsequently reduced dispersal and gene flow of a wetland butterfly, the US federally endangered St. Francis’ satyr butterfly (Neonympha mitchellii francisci). We surveyed nine populations throughout the taxon’s range using five polymorphic microsatellite loci. We found that genetic diversity of N. m. francisci was relatively high despite its restricted distribution, and that there is little evidence of population bottlenecks or extensive inbreeding within populations. We found substantial gene flow and detectable first generation migration, suggesting that N. m. francisci is unlikely to be currently endangered by genetic factors. Pairwise population differentiation and clustering indicate some structuring between populations on different drainages and suggest that dispersal probably occurs mainly via a stepping stone from the closest riparian corridors. However, genetic differentiation between geographically close populations suggests that isolation by distance is not solely responsible for population structure, and that management actions should be targeted at maintaining connectivity of riparian and upland habitats.     

Islands within islands: two montane palaeo‐endemic birds impacted by recent anthropogenic fragmentation

Anthropogenic habitat fragmentation of species that live in naturally patchy metapopulations such as mountaintops or sky islands experiences two levels of patchiness. Effects of such multilevel patchiness on species have rarely been examined. Metapopulation theory suggests that patchy habitats could have varied impacts on persistence, dependent on differential migration. It is not known whether montane endemic species, evolutionarily adapted to natural patchiness, are able to disperse between anthropogenic fragments at similar spatial scales as natural patches. We investigated historic and contemporary gene flow between natural and anthropogenic patches across the distribution range of a Western Ghats sky‐island‐endemic bird species complex. Data from 14 microsatellites for 218 individuals detected major genetic structuring by deep valleys, including one hitherto undescribed barrier. As expected, we found strong effects of historic genetic differentiation across natural patches, but not across anthropogenic fragments. Contrastingly, contemporary differentiation (D_PS) was higher relative to historic differentiation (F_ST) in anthropogenic fragments, despite the species’ ability to historically traverse shallow valleys. Simulations of recent isolation resulted in high D_PS/F_ST values, confirming recent isolation in Western Ghats anthropogenic fragments and also suggesting that this ratio can be used to identifying recent fragmentation in the context of historic connectedness. We suggest that in this landscape, in addition to natural patchiness affecting population connectivity, anthropogenic fragmentation additionally impacts connectivity, making anthropogenic fragments akin to islands within natural islands of montane habitat, a pattern that may be recovered in other sky‐island systems.     

Effects of dams and their environmental impacts on the genetic diversity and connectivity of freshwater mussel populations in Poyang Lake Basin,China

1. Habitat fragmentation is one of the main threats to biodiversity. Barriers to dispersal caused by anthropogenic habitat alteration may affect phylogeographic patterns in freshwater mussels. Knowledge of the phylogenetic and phylogeographic patterns of unionoids is vital to inform protection of their biodiversity.
2. Here, we assessed influences of dams and their environmental effects on the genetic diversity and population connectivity of a broadly distributed freshwater mussel, Nodularia douglasiae, in Poyang Lake Basin.
3. The results showed high genetic diversity in areas without dams and low genetic diversity in areas with dams. High genetic differentiation and low gene flow were found among the 11 populations. Genetic variation was significantly correlated with dissolved oxygen levels.
4. The observation of low genetic diversity in populations separated by dams indicated that those populations were subjected to genetic erosion and demographic decline because they are disconnected from other populations with higher diversity. High genetic differentiation and low gene flow among the 11 populations could be correlated with anthropogenic habitat alteration.
5. These results indicated that anthropogenic habitat alterations have led to the decline in freshwater mussel diversity. Therefore, we recommend maintaining favourable habitat conditions and connectivity of rivers or lakes, and strengthening study of life histories with host-test experiments to identify potential host fish species to strengthen the knowledge base underpinning freshwater mussel conservation.

     

Habitat fragmentation in forests affects relatedness and spatial genetic structure of a native rodent,Rattus lutreolus

Habitat fragmentation can have a range of negative demographic and genetic impacts on disturbed populations. Dispersal barriers can be created, reducing gene flow and increasing population differentiation and inbreeding in isolated habitat remnants. Aggregated retention is a form of forestry that retains patches of forests as isolated island or connected edge patches, with the aim of ‘lifeboating’ species and processes, retaining structural features and improving connectivity. Swamp rats (Rattus lutreolus) are a cover‐dependent species that are sensitive to habitat removal. We examined the effects of aggregated retention forestry and forestry roads in native wet Eucalyptus forests on swamp rat gene flow and population genetic structure. We characterized neighbourhood size in unlogged forest to provide a natural state for comparison, and examined population structure at a range of spatial scales, which provided context for our findings. Tests of pairwise relatedness indicated significant differentiation between island and edge populations in aggregated retention sites, and across roads in unlogged sites. Spatial autocorrelation suggested a neighbourhood size of 42–55 m and revealed male‐biased dispersal. We found no genetic isolation by geographical distance at larger (>2.3 km) scales and populations were all significantly differentiated. Our results suggest that removal of mature forest creates barriers for swamp rat dispersal. In particular, roads may have long‐term impacts, while harvesting of native forests is likely to create only short‐term dispersal barriers at the local scale, depending on the rate of regeneration.     

Hierarchical analysis of genetic structure in the habitat‐specialist Eastern Sand Darter (Ammocrypta pellucida)

Quantifying spatial genetic structure can reveal the relative influences of contemporary and historic factors underlying localized and regional patterns of genetic diversity and gene flow – important considerations for the development of effective conservation efforts. Using 10 polymorphic microsatellite loci, we characterize genetic variation among populations across the range of the Eastern Sand Darter (Ammocrypta pellucida), a small riverine percid that is highly dependent on sandy substrate microhabitats. We tested for fine scale, regional, and historic patterns of genetic structure. As expected, significant differentiation was detected among rivers within drainages and among drainages. At finer scales, an unexpected lack of within‐river genetic structure among fragmented sandy microhabitats suggests that stratified dispersal resulting from unstable sand bar habitat degradation (natural and anthropogenic) may preclude substantial genetic differentiation within rivers. Among‐drainage genetic structure indicates that postglacial (14 kya) drainage connectivity continues to influence contemporary genetic structure among Eastern Sand Darter populations in southern Ontario. These results provide an unexpected contrast to other benthic riverine fish in the Great Lakes drainage and suggest that habitat‐specific fishes, such as the Eastern Sand Darter, can evolve dispersal strategies that overcome fragmented and temporally unstable habitats.     

Landscape genetic structure of coastal tailed frogs (Ascaphus truei) in protected vs. managed forests

Habitat loss and fragmentation are the leading causes of species’ declines and extinctions. A key component of studying population response to habitat alteration is to understand how fragmentation affects population connectivity in disturbed landscapes. We used landscape genetic analyses to determine how habitat fragmentation due to timber harvest affects genetic population connectivity of the coastal tailed frog (Ascaphus truei), a forest-dwelling, stream-breeding amphibian. We compared rates of gene flow across old-growth (Olympic National Park) and logged landscapes (Olympic National Forest) and used spatial autoregression to estimate the effect of landscape variables on genetic structure. We detected higher overall genetic connectivity across the managed forest, although this was likely a historical signature of continuous forest before timber harvest began. Gene flow also occurred terrestrially, as connectivity was high across unconnected river basins. Autoregressive models demonstrated that closed forest and low solar radiation were correlated with increased gene flow. In addition, there was evidence for a temporal lag in the correlation of decreased gene flow with harvest, suggesting that the full genetic impact may not appear for several generations. Furthermore, we detected genetic evidence of population bottlenecks across the Olympic National Forest, including at sites that were within old-growth forest but surrounded by harvested patches. Collectively, this research suggests that absence of forest (whether due to natural or anthropogenic changes) is a key restrictor of genetic connectivity and that intact forested patches in the surrounding environment are necessary for continued gene flow and population connectivity.     

Connectivity of prairie dog colonies in an altered landscape: inferences from analysis of microsatellite DNA variation

Connectivity of populations influences the degree to which species maintain genetic diversity and persist despite local extinctions. Natural landscape features are known to influence connectivity, but global anthropogenic landscape change underscores the importance of quantifying how human-modified landscapes disrupt connectivity of natural populations. Grasslands of western North America have experienced extensive habitat alteration, fragmenting populations of species such as black-tailed prairie dogs (Cynomys ludovicianus). Population sizes and the geographic range of prairie dogs have been declining for over a century due to habitat loss, disease, and eradication efforts. In many places, prairie dogs have persisted in the face of emerging urban landscapes that carve habitat into smaller and smaller fragments separated by uninhabitable areas. In extreme cases, prairie dog colonies are completely bounded by urbanization. Connectivity is particularly important for prairie dogs because colonies suffer high probabilities of extirpation by plague, and dispersal permits recolonization. Here we explore connectivity of prairie dog populations using analyses of 11 microsatellite loci for 9 prairie dog colonies spanning the fragmented landscape of Boulder County, Colorado. Isolation-by-resistance modeling suggests that wetlands and high intensity urbanization limit movement of prairie dogs. However, prairie dogs appear to move moderately well through low intensity development (including roads) and freely through cropland and grassland. Additionally, there is a marked decline in gene flow between colonies with increasing geographic distance, indicating isolation by distance even in an altered landscape. Our results suggest that prairie dog colonies retain some connectivity despite fragmentation by urbanization and agricultural development.     

Long-Distance Dispersal of a Rescued Wolf From the Northern Apennines to the Western Alps

ABSTRACT By using Global Positioning System technology, we documented the long-distance dispersal of a wolf (Canis lupus) from the northern Apennines in Italy to the western Alps in France. This is the first report of long-distance dispersal of wolves in the human-dominated landscapes of southern Europe, providing conclusive evidence that the expanding wolf population in the Alps originates from the Apennine source population through natural recolonization. By crossing 4 major 4-lane highways, agricultural areas, and several regional and provincial jurisdictions, the dispersal trajectory of wolf M15 revealed a single, narrow linkage connecting the Apennine and the Alpine wolf populations. This connectivity should be ensured to allow a moderate gene flow between the 2 populations and counteract potential bottleneck effects and reduced genetic variability of the Alpine wolf population. The case we report provides an example of how hard data can be effective in mitigating public controversies originating from the natural expansion and recolonization processes of large carnivore populations. In addition, by highlighting the connectivity between these 2 transboundary wolf populations, we suggest that documenting long-distance dispersal is particularly critical to support population-based, transboundary management programs.     

Influence of Roads,Rivers, and Mountains on Natal Dispersal of White-Tailed Deer

Abstract: Natural and anthropogenic landscape features, such as rivers, mountain ranges, and roads can alter animal dispersal paths and movement patterns. Consequently landscape, through its effects on dispersal, may influence many ecological processes, including disease transmission, invasion dynamics, and gene flow. To investigate influences of landscape features on dispersal patterns of a large mammal, we captured and radiomarked 363 juvenile male white-tailed deer (Odocoileus virginianus), including 212 confirmed dispersers, in 2 topographically dissimilar study areas in Pennsylvania, USA. Dispersal azimuths were uniformly distributed in the western study area (WSA), where there was irregular, hilly topography. Mean dispersal azimuths paralleled ridge direction in the eastern study area, where long parallel ridges were aligned northeast-southwest. Major roads in both areas and a large river in the WSA were semipermeable barriers to dispersal of juvenile males; dispersal paths were less likely to intersect these linear features. Dispersal movements were direct and brief, typically lasting <12 hours. For all dispersers, we found no evidence for preference or avoidance of establishing adult, postdispersal ranges in proximity to roads; however, deer that encountered roads near the terminus of their dispersal path were more likely to stop on the near side. Further, for deer that established postdispersal home ranges near major roads, these features influenced range placement such that locations were typically clustered on one side of the road. The influence of roads, rivers, and mountains on dispersal paths and postdispersal locations of white-tailed deer suggest that landscape-specific features should be considered in conservation and management of this and possibly other species of large mammals.     

Gene flow in an endangered willow <Emphasis Type="Italic">Salix hukaoana</Emphasis> (Salicaceae) in natural and fragmented riparian landscapes

Salix hukaoana is an endangered riparian pioneer tree that is distributed within a restricted area of Japan. Microsatellite genetic variations and genetic structures were investigated in 80 subpopulations patchily distributed within five river basins with varying degrees of habitat fragmentation. The correlation between geographic distance and genetic distance based on the Bayesian assignment test was significant across relatively intact riparian habitats, with steeper slopes of regression for more densely grouped subpopulations, suggesting restricted gene flow. However, the correlation became less apparent with increasing spacing of the habitat patches. These contradictory results are attributed to the increased chance of long-distance dispersal of sexual propagules among more isolated habitat patches. The observed accumulation of genetic diversity with increasing distance downstream along a few, but not all, of the rivers and the results of assignment tests suggested a downstream directionality of gene flow. The results of this study illustrate the patterns of genetic diversity and contemporary dispersal of S. hukaoana, and provide important insights into understanding the gene dispersal of riparian trees and into the conservation of genetic resources for this species.     

A multiscale analysis of gene flow for the New England cottontail,an imperiled habitat specialist in a fragmented landscape

Landscape features of anthropogenic or natural origin can influence organisms' dispersal patterns and the connectivity of populations. Understanding these relationships is of broad interest in ecology and evolutionary biology and provides key insights for habitat conservation planning at the landscape scale. This knowledge is germane to restoration efforts for the New England cottontail (Sylvilagus transitionalis), an early successional habitat specialist of conservation concern. We evaluated local population structure and measures of genetic diversity of a geographically isolated population of cottontails in the northeastern United States. We also conducted a multiscale landscape genetic analysis, in which we assessed genetic discontinuities relative to the landscape and developed several resistance models to test hypotheses about landscape features that promote or inhibit cottontail dispersal within and across the local populations. Bayesian clustering identified four genetically distinct populations, with very little migration among them, and additional substructure within one of those populations. These populations had private alleles, low genetic diversity, critically low effective population sizes (3.2–36.7), and evidence of recent genetic bottlenecks. Major highways and a river were found to limit cottontail dispersal and to separate populations. The habitat along roadsides, railroad beds, and utility corridors, on the other hand, was found to facilitate cottontail movement among patches. The relative importance of dispersal barriers and facilitators on gene flow varied among populations in relation to landscape composition, demonstrating the complexity and context dependency of factors influencing gene flow and highlighting the importance of replication and scale in landscape genetic studies. Our findings provide information for the design of restoration landscapes for the New England cottontail and also highlight the dual influence of roads, as both barriers and facilitators of dispersal for an early successional habitat specialist in a fragmented landscape.     

Fine scale patterns of migration and gene flow in the endangered mound spring snail, <Emphasis Type="Italic">Fonscochlea accepta</Emphasis> (Mollusca:Hydrobiidae) in arid Australia

Naturally patchy ecosystems are models for other systems currently undergoing anthropogenic habitat fragmentation. Understanding patterns of gene flow in these model systems can help us manage species and ecosystems threatened by human impacts. The mound springs of central Australia represent such a natural model ecosystem, supporting a unique aquatic fauna distributed within an inhospitable arid landscape. Moreover, these springs are being impacted by over extraction of groundwater, providing a unique opportunity to look at dispersal in a patchy habitat that is changing. The present study represents the first fine scale analysis of gene flow under different scenarios of habitat connectivity for the endangered mound spring snail, Fonscochlea accepta. Within a single spring group pairwise estimates of F _ST between springs were very low (ave 0.015) with no association found between genetic distance and a series of geographical distance matrices based on the degree of habitat connectivity among the springs: results implying unstructured dispersal and limited population isolation. However, results from Bayesian assignment tests showed that on average approximately 97% of snails were assigned to their spring of origin. In a preliminary analysis at broader geographic scales (among spring groups) the results from F _ST estimates, Mantel correlation analyses and assignment tests all suggest much stronger and geographically correlated population structuring. While varying results from F-statistics and Bayesian analyses stem from the different information they utilise, together they provide data on contemporary and historical estimates of gene flow and the influence of landscape dynamics on the spatial genetic patterning of the springs.     

Limited influence of local and landscape factors on finescale gene flow in two pond‐breeding amphibians

Dispersal and gene flow within animal populations are influenced by the composition and configuration of the landscape. In this study, we evaluated hypotheses about the impact of natural and anthropogenic factors on genetic differentiation in two amphibian species, the spotted salamander (Ambystoma maculatum) and the wood frog (Lithobates sylvaticus) in a commercial forest in central Maine. We conducted this analysis at two scales: a local level, focused on factors measured at each breeding pond, and a landscape level, focused on factors measured between ponds. We investigated the effects of a number of environmental factors in six categories including Productivity, Physical, Land Composition, Land Configuration, Isolation and Location. Embryos were sampled from 56 spotted salamander breeding ponds and 39 wood frog breeding ponds. We used a hierarchical Bayesian approach in the program GESTE at each breeding pond and a random forest algorithm in conjunction with a network analysis between the ponds. We found overall high genetic connectivity across distances up to 17 km for both species and a limited effect of natural and anthropogenic factors on gene flow. We found the null models best explained patterns of genetic differentiation at a local level and found several factors at the landscape level that weakly influenced gene flow. This research indicates multiscale investigations that incorporate local and landscape factors are valuable for understanding patterns of gene flow. Our findings suggest that dispersal rates in this system are high enough to minimize genetic structuring and that current forestry practices do not significantly impede dispersal.     

Fine‐scale genetic structure in an eastern Alpine black grouse Tetrao tetrix metapopulation

Understanding genetic consequences of habitat fragmentation is crucial for the management and conservation of wildlife populations, especially in case of species sensitive to environmental changes and landscape alteration. In central Europe, the Alps are the core area of black grouse Tetrao tetrix distribution. There, black grouse dispersal is limited by high altitude mountain ridges and recent black grouse habitats are known to show some degree of natural fragmentation. Additionally, substantial anthropogenic fragmentation has occurred within the past ninety years. Facing losses of peripheral subpopulations and ongoing range contractions, we explored genetic variability and the fine‐scale genetic structure of the Alpine black grouse metapopulation at the easternmost fringe of the species’ Alpine range. Two hundred and fifty tissue samples and non‐invasive faecal and feather samples of eleven a priori defined subpopulations were used for genetic analysis based on nine microsatellite loci. Overall, eastern Alpine black grouse show similar amounts of genetic variation (H_O = 0.65, H_E = 0.66) to those found in more continuous populations like in Scandinavia. Despite of naturally and anthropogenically fragmented landscapes, genetic structuring was weak (global F_ST < 0.05), suggesting that the actual intensity of habitat fragmentation does not completely hamper dispersal, but probably restricts it to some extent. The most peripheral subpopulations at the edge of the species range show signs of genetic differentiation. The present study gives new insights into the population genetic structure of black grouse in the eastern Alps and provides a more fine‐scale view of genetic structure than previously available. Our findings will contribute to monitor the current and future status of the population under human pressures and to support supra‐regional land use planning as well as decision making processes in responsibilities of public administration.     

Landscape effects on the contemporary genetic structure of Ruffed Grouse (Bonasa umbellus) populations

The amount of dispersal that occurs among populations can be limited by landscape heterogeneity, which is often due to both natural processes and anthropogenic activity leading to habitat loss or fragmentation. Understanding how populations are structured and mapping existing dispersal corridors among populations is imperative to both determining contemporary forces mediating population connectivity, and informing proper management of species with fragmented populations. Furthermore, the contemporary processes mediating gene flow across heterogeneous landscapes on a large scale are understudied, particularly with respect to widespread species. This study focuses on a widespread game bird, the Ruffed Grouse (Bonasa umbellus), for which we analyzed samples from the western extent of the range. Using three types of genetic markers, we uncovered multiple factors acting in concert that are responsible for mediating contemporary population connectivity in this species. Multiple genetically distinct groups were detected; microsatellite markers revealed six groups, and a mitochondrial marker revealed four. Many populations of Ruffed Grouse are genetically isolated, likely by macrogeographic barriers. Furthermore, the addition of landscape genetic methods not only corroborated genetic structure results, but also uncovered compelling evidence that dispersal resistance created by areas of unsuitable habitat is the most important factor mediating population connectivity among the sampled populations. This research has important implications for both our study species and other inhabitants of the early successional forest habitat preferred by Ruffed Grouse. Moreover, it adds to a growing body of evidence that isolation by resistance is more prevalent in shaping population structure of widespread species than previously thought.