Comparative biogeography of volant and nonvolant mammals in a temperate island archipelago

Island biogeography theory is a foundational ecological concept that describes how island or habitat patch size and isolation predict biodiversity, but few have studied how the effects of island biogeography vary with life history characteristics of temperate mammal communities. From 2014 to 2020, we surveyed volant and nonvolant mammals within the Apostle Islands archipelago (Wisconsin, USA) using camera trapping, live trapping, and acoustic monitoring. We used linear regression and information-theoretic model selection to evaluate the effects of island size and isolation on indices of biodiversity. We also examined the effects of life history characteristics (i.e., body mass, winter inactivity) on the relative abundance and distribution of each species on the islands and the mainland. For volant mammals, island size and isolation were not associated with any metrics of diversity. We found island size was positively associated with nonvolant mammal species richness and diversity, but not species evenness. Island isolation was not a significant predictor for small nonvolant mammal diversity, although both size and isolation appeared to influence island biogeography of medium-large nonvolant mammals. We also found that the interaction between winter inactivity and body mass influenced the vagility of nonvolant mammals in the archipelago. Our results suggest that life history characteristics are important in mediating species responses to biogeography, supporting the dispersal-limitation nonequilibrium view of island biogeography theory, particularly for nonvolant mammals.