Linking Mate Choice to Hearing and Ear Structure in Engystymops (Physalaemus) petersi
Differences in response to acoustic signals can result from changes to ear structures, and consequently hearing sensitivity, or differences in central processing. This study investigated the mechanisms underlying differences in female call preference of three closely related anuran species of the species complex Engystymops petersi. Amongst the species investigated, males differ in their call frequencies used for mate signaling and females differ in their preferences for those calls, with consistent preference for conspecific calls. Using auditory brainstem recordings and histology, we examined how closely the hearing of female anurans corresponds to conspecific male call frequencies and whether morphological differences in the ear could explain hearing differences among the three species. Our data shows that females from these three species differ in hearing sensitivity as well as in ear morphology. However, inner ear volume, middle ear volume, columella volume, and tympanum size correlate with differences in head width and do not vary between species in ways that explain differences in hearing sensitivity. Our results indicate that a change in peripheral sensitivity could contribute to behavioral differences in mate preference of closely related anuran species.
Womack, M.C., Brandt, C. and Christensen-Dalsgaard, J., and Hoke, K.L., Linking mate choice to hearing and ear structure in Engystymops (Physalaemus) petersi. Evolution. 2012. Ottawa, Canada. (poster)