Evolution of the advertisement call in neotropical frogs : patterns and drivers

Abstract

Anuran males emit advertisement calls to attracting mates and repelling conspecific males. Such calls are genetically determined, stereotyped, and subjected to evolutionary forces. It is expected that the evolution of call traits is associated with the evolution of anatomical traits, as well as the acoustics of the environment. We aim to study the patterns of evolution of the advertisement call in Neotropical frogs as well as their potential drivers through two approaches: a macroevolutionary approach to study the evolution of advertisement calls in a phenotypically diverse clade tree frogs (Hylidae: Cophomantini); and an experimental approach to study associations between habitat features and acoustic transmission of advertisement calls in an anuran community. In the first approach, we applied phylogenetic comparative analyses to study the relative roles of shared ancestry, body size, calling site, vegetation structure, and characteristics of lotic environments on the evolution of acoustic traits in Cophomantini, and assessed the tempo and mode of evolution of acoustic and morphometric traits. We used the latest molecular phylogeny for the group, advertisement call recordings from sound collections and fieldwork, morphometric data from museum specimen and published data, as well as calling sites and species distributions to carry out phylogenetic comparative analyses. We found no support for the predictions of Evolution correlation with the environment, but a significant correlation between body size and peak frequency, which is consistent with the results of previous studies that support a strong association between variation in size and spectral call traits. Our study shows that acoustic traits differ in the tempo and mode of evolution in relation to morphometric traits, indicating a different evolutionary path. For the second approach, we carried out sound transmission experiments, using calls of three species (Boana bischoffi, B. leptolineata and Hylodes meridionalis) from an anuran community in Southern Brazil. We hypothesized that call attenuation is reduced in the native forest, since species evolved in this environment. Our results show that the advertisement calls of the two Boana species attenuate lesser in timberlands than in the native forest, while the third species shows either no differences or less attenuation in native forests. All our results provide empirical contributions to future studies dissect the mechanism that explain the evolution of anuran calls