Gliding towards an understanding of the origin of flight in bats

Bats are the only mammals capable of powered flight and have correspondingly specialized body plans, particularly in their limb morphology. The evolution of bat flight is still not fully understood due to an uninformative fossil record, but it is widely hypothesized that flying evolved from gliding. Here, we test the gliding to flying hypothesis of the origin of bat flight by using phylogenetic comparative methods to model the evolution of forelimb and hind limb traits on a dataset spanning four extinct bats and 231 extant mammals with diverse locomotor regimes. Our results reveal gliders’ elongate forelimb adaptive optima to be intermediate between those of bats and arborealists and that gliders and bats share a single adaptive zone characterized by elongate and narrow hind limb traits. Together, our results inform how glider-like postcranial morphology may have gradually evolved into bat-like morphology prior to powered-flight behavior. Finally, we propose a hypothetical adaptive landscape based on the length and width optima trends that we interpret considering the macroevolutionary transition from arborealism to gliding to flying in mammals.