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 landscape 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 and additionally used nuclear microsatellite markers for the pine marten. A total of 211 individuals (29 pine martens and 182 stone martens) from both mainland and island populations were analysed. For pine marten, we found a significant genetic structuring, with pronounced differentiation between island and mainland populations, and a further substructure within the mainland. No significant isolation by distance was detected (Mantel test, p = 0.15), suggesting that genetic differentiation is driven more by habitat discontinuities and anthropogenic barriers rather than geographical distance alone. In contrast, stone marten exhibited weak genetic structure and high genetic diversity, indicating gene flow and potential landscape permeability for this more synanthropic species. These contrasting patterns underscore species-specific responses to landscape fragmentation and highlight the need to tailor management strategies accordingly.