Neural and behavioral responses to reproductive signals in male chorus frogs.

Species recognition and courtship behaviors are powerful drivers of speciation. Here, we investigated the neural and behavioral signatures of species recognition in Upland chorus frogs (Pseudacris feriarum). Populations of this species that are sympatric with congeners (e.g. Pseudacris nigrita) have evolved divergent male mating calls and enhanced acoustic discrimination by females owing to costly interspecific hybridization. Herein, we examined evoked neural activity and behaviors in male P. feriarum in response to sympatric, allopatric or heterospecific calls, or silence, via phospho-S6 ribosomal protein immunofluorescence. The sympatric call evoked activity in several brain regions that regulate spatial navigation and social decision making, indicating that this call type may be an important trigger for navigating to and within a complex chorus environment. Moreover, each stimulus resulted in a unique pattern of coactivation among brain regions. Despite these neural changes, there were no differences in behavioral response to each stimulus. Our results suggest that signal input and behavioral output are coded independently in the brains of male chorus frogs. Together, these findings represent a first step towards understanding the neural basis of conspecific recognition in a system in which this trait contributes to ongoing diversification.