First insight into genetic diversity of two sympatric marten species between the Alps and Adriatic islands

Closely related species occupying the same geographical area may exhibit markedly different genetic patterns due to differences in evolutionary history, ecology and behaviour. In this study, a population genetics approach is applied to investigate the genetic structure, diversity, and connectivity of two sympatric carnivore species, i.e., the European pine marten (Martes martes) and the stone marten (Martes foina) in Croatia and Slovenia. We analysed mitochondrial DNA sequences for both species (28 pine marten and 104 stone marten samples, respectively) and additionally investigated nuclear microsatellite markers for 182 stone martens. For stone marten, we found a significant genetic structuring, with pronounced differentiation between island and mainland populations, and a further substructure within the mainland. But no significant isolation by distance was detected (Mantel test, p = 0.15), indicating that differentiation is primarily shaped by island-mainland separation and other geographical discontinuities rather than by distance alone. In contrast, pine marten exhibited moderate haplotype diversity and limited spatial resolution due to the smaller sample size. These contrasting patterns underscore species-specific responses to natural geographical barriers and highlight the need to tailor management strategies accordingly.