The complex evolutionary history of the tympanic middle ear in frogs and toads (Anura)
PEREYRA, M.O.; WOMACK, M.C.; BARRIONUEVO, J.S.; BLOTTO, B. L.; BALDO, D.; TARGINO, M.; OSPINA-SARRIA, J.J.; GUAYASAMIN, J.M.; COLOMA, L.A.; HOKE, K.L.; GRANT, T.; FAIVOVICH, J.
Año: 2016 vol. 6 p. 1 - 1
Most anurans possess a tympanic middle ear (TME) that transmits sound waves to the inner ear;however, numerous species lack some or all TME components. To understand the evolution ofthese structures, we undertook a comprehensive assessment of their occurrence across anuransand performed ancestral character state reconstructions. Our analysis indicates that the TME wascompletely lost at least 38 independent times in Anura. The inferred evolutionary history of the TME isexceptionally complex in true toads (Bufonidae), where it was lost in the most recent common ancestor,preceding a radiation of >150 earless species. Following that initial loss, independent regains of someor all TME structures were inferred within two minor clades and in a radiation of >400 species. Thereappearance of the TME in the latter clade was followed by at least 10 losses of the entire TME. Themany losses and gains of the TME in anurans is unparalleled among tetrapods. Our results show thatanurans, and especially bufonid toads, are an excellent model to study the behavioural correlates ofearlessness, extratympanic sound pathways, and the genetic and developmental mechanisms thatunderlie the morphogenesis of TME structures.