Convergent deployment of ancestral programs during the evolution of mammalian flight membranes

Lateral flight membranes, or patagia, have evolved repeatedly in diverse mammalian lineages. While little is known about patagium development, its recurrent evolution may suggest a shared molecular basis. By combining transcriptomics, developmental experiments, and mouse transgenics, we demonstrate that lateral WNT5A expression in the marsupial sugar glider (Petaurus breviceps) promotes the differentiation of its patagium primordium. We further show that this function of WNT5A reprises ancestral roles in skin morphogenesis predating mammalian flight and has been convergently employed during patagium evolution in eutherian bats. Moreover, we find that many genes involved in limb development have been re-deployed during patagium outgrowth in both the sugar glider and bat. Taken together, our findings reveal that deeply conserved molecular toolkits underpin the evolutionary transition to flight in mammals.