Depauperate Small Mammal Assemblages in the National Park Protecting Land-Bridge Island Habitats Are Shaped More by Topography than Plant Communities

Small mammal species assemble based mainly on plant communities but the structure of their assemblages is shaped by several other factors, modified by larger-scale geography. Despite their ecological significance, they are often neglected elements of biodiversity, therefore, even several Polish national parks have lacked extensive surveys. It also applies to the Wolin National Park (WNP), the only one located on a coastal marine island, known previously for its unique bat fauna. We surveyed small mammals of WNP by live- and pitfall trapping, identifying only nine species, the lowest species richness among five national parks of the region (the remaining hosted 11-13 species, based on trapping data only) and the rarefaction curve showed very low probability of increasing that number by future sampling. Such unexpected paucity of species is probably linked to insular isolation and the location of the park at the edge of regional distributions of the three species. Cluster analysis revealed the most peculiar feature of small mammal assemblages in WNP - a division of the Park into two landscape units, moraine hills and the alluvial delta, where predominant murids were, respectively, Apodemus flavicollis and Apodemus agrarius. That divergence appeared to affect the clustering more than vegetation at the trapping sites.