Evolution of the unique vocal sacs of casque-headed treefrogs

AGUSTIN JORGE ELIAS COSTA; IVAN NUNES; JULIÁN FAIVOVICH; PEGRO H. A. G. MOURA

Congreso; I Meeting of Systematics, Biogeography and Evolution (SBE); 2020

Vocal sacs are among the most conspicuous features of anurans, and in casque-headed treefrogs of the tribe Lophyohylini (Hylidae), they are particularly striking. They include a wide array of morphologies that range from single subgular structures to paired, dorsolaterally-projecting lobes that are unique in Anura. Morphology of the vocal sacs has traditionally played a role in the taxonomy of the group, but the condition of many species, as well as how they relate to the iconic vocal sacs of most Trachycephalus, are still poorly known. Herein we assessed the anatomy of representatives of Lophyohylini and studied their evolution in all 87 currently-recognized species. Also, we discuss how variations of the internal structure affect the shape of the inflated vocal sac, something that can be extended to the majority of species of Anura. We obtained a strong correlation between vocal sac morphology and breeding site, with at least some degree of reduction being present in all ten independent origins of phytotelm-breeding in the tribe, showing unprecedented levels of plasticity for this structure. Moreover, we provide insights into the evolution of paired lateral vocal sacs in Anura, and how the characteristic structures of most Trachycephalus differ from those of other distantly-related groups.