The evolution of contact pheromones in Odontomachus trap-jaw ants

Communication via cuticular hydrocarbons is widespread throughout solitary and eusocial insects. For many solitary insects, cuticular hydrocarbons convey mate and species recognition signals. For eusocial insects, hydrocarbon signals encode information essential to colony organization: nestmate signals, caste and sex cues, and individual fertility status. Understanding how selection works on multiple signals encoded within a single phenotype is a crucial step in understanding the evolution of chemical communication and the maintenance complex phenotypic traits. Our studies of the trap-jaw ant, Odontomachus brunneus, provide experimental evidence that a single chemical phenotype includes components responsible for signaling fertility and nestmate status, as well as sex. We discovered that, within this species, the cuticular hydrocarbon profile is highly divergent across populations; however the cuticular hydrocarbon signal for fertility has been conserved across populations. Furthermore, we document male-specific cuticular hydrocarbon profiles. We show that male-specific hydrocarbon patterns are also conserved across these populations despite divergence in the overall profile. Our results are summarized in a discussion of how a single phenotype can diverge across populations while selection conserves specific signals within that phenotype.