Speciation, sexual selection, and the macroevolution of cricket mating signals

Animal mating signals can communicate both species-specific recognition information and male phenotypic quality persuasion information to females. Here we show that the recognition components of cricket song diverge early and rapidly among species pairs, especially so among those pairs with the potential for gene flow compared to allopatric pairs. Divergence in the persuasion components of song is less closely linked to speciation. Together these results suggest that the key mating signal recognition traits involved in speciation evolve in a punctuated manner, and at equilibrium are subject to stabilizing selection. Persuasion traits, on the other hand, are typically under directional sexual selection, but are not the traits closely tied to speciation. This suggests that the mechanistic link between sexual selection and speciation is ephemeral, based on rapid change in recognition traits during speciation. An important implication is that equilibrium within-population sexual selection is uncoupled from interspecific divergence during speciation. We expect that the distinction between recognition and persuasion traits, and the particular importance of divergence in recognition traits for speciation, should be a widespread phenomenon.