Behavioral Components of Sex Role Reversal in the Tettigoniid Bushcricket Ephippiger ephippiger

Abstract

Facultative sex role reversal is found in species of tettigoniid bushcrickets in which males invest heavily in matings or offspring by producing large, nutritious spermatophores. On high-quality diets such species show conventional sex roles, but under low-quality diets males become the choosier sex. Comparative work suggests that Ephippiger ephippiger (Tettigoniidae, Ephippigerinae) has one of the largest described spermatophores (up to 40% of the male body weight). Here we examine the behavior of this species under variable diet conditions in the laboratory and find evidence of sex role reversal under poor-quality diet conditions. We also examine the behavioral components of sex role reversal. In the reversed condition, rejections of mating attempts are almost solely by the male and contests are almost solely between females. Role-reversed males sing less frequently and at a much reduced intensity. We use geographic variation in the calling song of this species to assess the strength of female phonotactic discrimination between races. This is not significantly reduced despite sex role reversal. We therefore suggest that the male and female aspects of the acoustic sexual communication system differ in that male components change most during facultative sex role reversal.