SPECIES RECOGNITION IS DRIVING EVOLUTION OF THE ACOUSTIC MATING SYSTEM OF SHIELD BACK KATYDIDS (ORTHOPTERA: TETTIGONIIDAE: AGLAOTHORAX): BEHAVIORAL AND PHYLOGENETIC EVIDENCE

Abstract

Sexual selection and species recognition are two processes that may drive evolution of mating systems and contribute to speciation. Evidence from nature is rare. I asked whether song evolution in shield-back katydids (Aglaothorax) from southern California is consistent with either of these processes. Analysis of male song recordings identified four variable characters, and revealed a song cline in the Transverse Ranges. Of the variable song characters, I estimated female preferences for pulse number and interpulse interval, the former with choice tests on a Y-maze and the latter with no-choice tests on a locomotion compensator. Females of two coexisting Transverse Range species each discriminated against the interpulse intervals of the other. Phylogenetic relationships inferred from nuclear gene fragments were used to reconstruct ancestral distributions and song evolution. Significantly higher rates of song evolution were shown for the species coexisting in response to secondary contact, results consistent with species recognition.