Sexual selection and population divergence III. Interspecific and intraspecific variation in mating signals

A major challenge for studying the role of sexual selection in divergence and speciation is understanding the relative influence of different sexually-selected signals on those processes in both intra and interspecific contexts. Different signals may be more or less susceptible to co-option for species identification depending on the balance of sexual and ecological selection acting upon them. To examine this, we tested three predictions to explain geographic variation in long- vs. short-range sexual signals across a 3,500+ km transect of two related Australian field cricket species (Teleogryllus spp.): 1) selection for species recognition, 2) environmental adaptation, and 3) stochastic divergence. We measured male calling song and male and female cuticular hydrocarbons (CHCs) in offspring derived from wild populations, reared under common garden conditions. Song clearly differentiated the species and no hybrids were observed suggesting that hybridisation is rare or absent. Spatial vari...