Perception and diversification of fertility signals in Odontomachus trap-jaw ants

The cuticular hydrocarbon profile encodes information essential to ant colony organization: nestmate signals, sex cues, and individual fertility status. Understanding the chemical nature of these signals and how multiple signals are encoded within a single phenotype are crucial steps in understanding the evolution of eusociality. My studies of North-American Odontomachus trap-jaw ants provide data on how queen and worker fertility is signaled and how these signals evolve both within and between species. For O. brunneus I provide experimental evidence that (Z)-9-nonacosene serves as the fertility signal for queens and workers. Across Florida populations, O. brunneus has divergent and population-specific cuticular hydrocarbon nestmate profiles, but the fertility signal is conserved. Treating non-reproductive workers with the fertility signal elicits queen-like reactions only when the reacting workers are from the same population. Similarly, live queens are treated as a queen only by workers from the same population. Finally, the fertility signal alone, without any other accompanying hydrocarbons fails to elicit queen-like responses from any workers. These results suggest that perception of the fertility signal is dependent on the presence of a nestmate or nestmate-like cuticular hydrocarbon profile. Finally, I examine the potential fertility signals used by closely related species, O. relictus, O. ruginodis, and O. haematodus. I find that fertility signals are not conserved across these closely related species. Surprisingly, I also report that the cuticular compounds that best distinguish a reproductive from a non-reproductive individual in O. ruginodis are compounds that were, before now, unknown to occur on any insect.