The studies in island biogeography of bats have shown relationships between species richness (SR) and island characteristics. However, focusing only on taxonomic diversity such as SR, it is difficult to infer the functional roles of ecological features and biotic interactions in structuring bat assemblages. Therefore, it is necessary to compare taxonomic diversity with functional diversity to understand how the biogeographical patterns of bats have been shaped. This study investigated the taxonomic and functional diversity patterns of Japanese insectivorous bats across 17 islands. To grasp how the composition of bats varies, we examined the relationships between the diversity indexes (alpha and beta diversity) and island characteristics (area and distance to the mainland).
Firstly, our analyses showed that SR and functional richness (FRic) significantly positively correlated with the island area, but the relationship was weaker in FRic than SR. There were no significant correlations between distance to the mainland and any diversity indexes. Secondly, the analyses of beta diversity indicated that the relative contribution of nested components was higher in functional diversity (48 %) than species diversity (32 %). These results suggest that functional traits might play a role in structuring bat assemblages.