Gliding towards an understanding of the origin of flight in bats

Abstract

AbstractBats are the only mammals capable of powered flight and have correspondingly specialized body plans, particularly in their limb morphology. The origin of bat flight is still not fully understood due to an uninformative fossil record, but it is widely hypothesized that bats evolved from gliding ancestors. Here, we test predictions of 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 non-gliding arborealists. Our results also show that gliders and bats share an adaptive zone characterized by elongate and narrow hind limb bones. We propose a hypothetical adaptive landscape based on skeletal length and width optima trends, which we interpret within our robust mammal limb dataset. Our results support the potential for glider-like postcranial morphology to evolve into bat-like morphology prior to powered-flight behavior, setting a foundation for future developmental, biomechanical, and evolutionary research to test this idea.