Therefore, the concept of isolation by resistance (IBR) is of particular interest in wildlife conservation genetics (McRae, 2006). However, the spatial genetic structure of wildlife species can be affected by several co-occurring factors and processes beyond Euclidean distances (Balkenhol et al., 2016). Isolation by distance (IBD) describes the positive relationship between genetic differentiation and geographic distance (usually driven by a species' dispersal Wright, 1943), a pattern commonly observed in panmictic populations (Sexton et al., 2014). Various frameworks and concepts can be applied to identify the spatial distribution of genetic data (Sexton et al., 2014 Wagner & Fortin, 2013 Wang & Bradburd, 2014) and are the basis to understand the structure of populations and infer management strategies. Particularly for species in fragmented landscapes, maintaining gene flow is of high relevance to preserve genetic diversity and minimize extinction risks of populations and species (Frankham et al., 2010). Spatial population genetic methods are increasingly used in modern wildlife ecology and conservation. Our study provides valuable insights into the spatial genetic variation of this small-scale metapopulation system of Alpine black grouse. The easternmost subpopulation was the most differentiated, and at the same time, immigration was not detected hence, its long-term survival might be threatened. Spatial genetic variation could be attributed to effects of isolation by distance among individuals and isolation by resistance among subpopulations, yet unknown effects might factor in. Although population genetic analyses revealed overall low levels of genetic differentiation, the ecological niche modeling showed subpopulations to be clearly delimited by habitat structures. We then applied regression-based approaches combined with population genetic analyses based on microsatellite data to disentangle effects of isolation by distance and isolation by resistance among individuals and subpopulations. Correlative ecological niche modeling was used to assess geographic distances and landscape resistances.
Here, we addressed whether the genetic pattern of the easternmost Alpine black grouse metapopulation system is driven by isolation by distance or isolation by resistance. Molecular data combined with spatial analyses can help to assess landscape effects on genetic variation and therefore can be informative for conservation management. At its easternmost Alpine range, events of subpopulation extinction have already been documented in the past decades. Within Central Europe, the Alps represent the core distribution area of the black grouse, Lyrurus tetrix. Especially for animal species in fragmented landscapes, preservation of gene flow becomes a high priority target in order to restore genetic diversity and prevent local extinction. In modern wildlife ecology, spatial population genetic methods are becoming increasingly applied.