Intraspecific variation in animal mating signals: a test of Mayr's conjecture

Mayr proposed that the stringency of stabilizing selection on animal mating signals is context-dependent: in species lacking sympatric congeners, relaxed selection pressure would afford greater intraspecific variability. This idea has rarely (if ever) been directly tested. Here, I evaluate Mayr's conjecture using a comprehensive dataset on acoustic mating signals from 39 taxa (33 named species and 6 unnamed lineages) of North American Gryllus field crickets. In doing so, I distinguish between 2 distinct functions of mating signal components: recognition versus persuasion. Contrary to Mayr's prediction, intraspecific variation in recognition mating signals did not increase in species with fewer or no sympatric congeners. Stabilizing selection on recognition traits appears to be maintained across both isolated and sympatric populations, possibly due to selection for efficient intraspecific communication-aligning with some aspects of Paterson's "Specific Mate Recognition System" model. Persuasion traits, on the other hand, show elevated levels of variation consistent with directional sexual selection promoting condition dependence. Together these results reveal the ubiquity of stabilizing selection on recognition traits when at evolutionary equilibrium, and the critical importance of distinguishing between recognition and persuasion functions of animal mating signals.