Evolution and ecology of body size in the world’s largest bats

Abstract

Pteropus and closely related flying fox genera in the subfamily Pteropodinae represent a remarkable radiation of insular taxa. Comprising more than 80 species, the group includes the largest living or extinct bat species. Exceptional vagility has allowed these bats to colonize numerous Pacific and Indian Ocean islands, where they play crucial ecological roles in maintaining ecosystems. It has long been noted that on islands where multiple species coexist, there is a tendency for size differentiation among them. We investigated this pattern in depth using skull length as a proxy for body size and analysing hundreds of data points across most species and islands. We employed a phylogenetic framework to evaluate the evolutionary processes driving size variation in Pteropus and Pteropodinae. We updated the molecular phylogeny to include most pteropodine species and applied phylogenetic comparative methods to evaluate different models of phenotypic evolution. Results suggest that natural selection, most likely through character displacement in islands, played a significant role in the evolution of body size in Pteropodinae. Additionally, other processes such as species sorting and ecological release may also have contributed to the observed pattern of size evolution.