Meeting Abstract

P1-65   -   Understanding the origin of bat flight: Evolutionary modeling of mammal limb morphologies Burtner, A*; Grossnickle, D; Santana, S; Law, C; University of Washington; University of Washington; University of Washington; University of Washington aburtner@uw.edu

Bats are the only mammals capable of powered flight and have correspondingly specialized body plans, apparent in the limbs. These specialized morphologies are thought to be the result of adaptations for the demands of flight; the skeletal elements of the bat forelimbs are elongated in order to support flight membranes and increase aerodynamic efficiency, whereas bat hind limbs are relatively short and specialized for hanging and catching prey in flight. Due to a deficient fossil record, the evolution of bat flight is still not fully understood, but is hypothesized to be the result of an ancestral transition from gliding to flying. This hypothesis is plausible considering the morphological similarities between bat and glider forelimbs (both elongated) and the contrast between bat and glider hind limbs (qualitatively shorter versus elongated). In this study, we collected linear measurements of the forelimb and hind limb skeletal elements of flying, gliding, arboreal, and terrestrial mammals. We then fit evolutionary models to the data to test the hypothesis that A) selective pressures for flight drove the evolution of bat forelimb skeletal elements from glider-like forelimbs, and that B) bat hind limbs evolved to become morphologically distinct from those of other mammals. If these hypotheses are supported, we predict that A) bat and glider forelimb trait optima will be located in the same region of morphospace and B) bat hind limb trait optima will be located in a unique region of morphospace. Preliminary results provide some support for these predictions; forelimb trait optima for gliders fall in a region of morphospace between generalists and bats and hind limb trait optima for bats fall in a distinct region in morphospace. This research helps address the longstanding question of how bat flight may have evolved from ancestral gliding mammals.