Data from: 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
variation in song was not predicted by geography, genetics or climatic
factors in either species. In contrast, CHC divergence was strongly
associated with an environmental gradient supporting the idea that the
climatic environment selects more directly upon these chemical signals. In
light of recently advocated models of diversification via ecological
selection on secondary sexual traits, the different environmental
associations we found for song and CHCs suggest that the impact of
ecological selection on population divergence, and how that influences
speciation, might be different for acoustic vs. chemical signals.