Putting the leaf-nosed bats in context: a geometric morphometric analysis of three of the largest families of bats

Bats in the family Phyllostomidae exhibit the most diverse dietary ecology of any mammalian family and the link between their morphology and diet is well-studied. However, the morphology of phyllostomids has yet to be placed into a broader context by comparing them to bats from other families through the use of geometric morphometrics. Using geometric morphometrics, we examined shape trends, disparity, and links between shape and diet using the crania and dentaries of 176 species from 3 of the largest bat families: Vespertilionidae, Molossidae, and Phyllostomidae. Results indicate that cranium shape in insectivorous phyllostomids does not overlap with non-phyllostomid families, suggesting at least 2 insectivorous cranial morphotypes have evolved within Chiroptera and phyllostomid cranial shape had already diverged from other bat families prior to developing their broad dietary range. Further, phyllostomids have higher cranium shape (1.5×) and dentary shape (1.89×) disparity than molossids and vespertilionids, whose dentary and cranium shape disparity is roughly equal. Although the cranium is constrained in many ways (e.g., housing the brain, vision, olfaction), we suggest the fact that dentary shape is limited to food processing allowed it to expand into larger regions of morphospace. Finally, a preliminary dietary analysis based on prey hardness indicates substantial shape overlap within families except for those species with extreme diets (e.g., liquid, very-hard food). Many bats are dietary generalists that eat a wide variety of food types of varying hardness. The data from the 3 large families of bats presented here suggest that eating foods of intermediate hardness may not require substantial cranial reorganization.