Sex differences in response to nonconspecific advertisement calls: receiver permissiveness in male and female túngara frogs

In many species, males advertise to both male and female audiences. Given the asymmetry in fitness costs of recognition errors in response to mating signals for the sexes, usually higher for females than males, males are expected to be more permissive than females in their responses to signals. Few studies, however, have investigated such differences and there is no consensus on which sex is more permissive to signal variation. We examined the evoked vocal responses of male túngara frogs, Physalaemus pustulosus, to 14 species of heterospecific and ancestral male mating calls to evaluate the influence of call similarity and phylogenetic distance on their responses. We also compared male calling responses to female phonotactic responses to examine the propensity of response errors between the sexes. Recognition errors were higher for males than females, as predicted by the different costs associated with recognition errors for each sex. Males responded to the calls of most species with mating calls, and produced aggressive calls in response to two other heterospecific/ancestral calls. The responses of males were explained by phylogenetic distance but not by overall call similarity. Similarly, females were more likely to show phonotaxis to calls of species and ancestors that were more closely related. Therefore, evolutionary history has left a perceptual footprint on the brain of both sexes but the details seem to differ. We discuss proximate reasons underlying sexual differences in receiver permissiveness in túngara frogs and potential factors leading to their evolution.