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

## TL;DR

This study tests a 60-year-old theory about mating signal variation in crickets and finds that stabilizing selection on recognition signals is consistent across species, while persuasion signals show more variation.

## Contribution

The paper is the first to directly test Mayr's conjecture and highlights the importance of distinguishing recognition and persuasion mating signals.

## Key findings

- Stabilizing selection on recognition mating signals is maintained regardless of sympatric congener presence.
- Persuasion traits show higher variation, likely due to directional sexual selection.
- The distinction between recognition and persuasion functions is critical for understanding mating signal evolution.

## Abstract

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.

This paper presents 2 significant advances of interest to a broad audience of biologists engaged in research on speciation and the evolution of reproductive isolation, sexual selection, and/or mating signal evolution. The 2 significant advances are (i) testing for the first time a 60+ year old prediction from Ernst Mayr regarding levels of variation in animal mating signals, and (ii) demonstrating empirically the importance of making a key distinction between recognition mating signals and persuasion mating signals, which despite being ∼75 years old (attributable to Niko Tinbergen), has largely been absent from modern discussions of mating signal evolution. The empirical work is based on phylogenetically informed analysis of an entire clade, so the findings apply broadly.