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
two 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.