Comparative genomics analyses reveal selection on neuronal and cuticular hydrocarbon genes is associated with aggression in ants (Hymenoptera: Formicidae)

Abstract

Aggression is an essential component of survival and fitness, although the expression of aggression behaviors can also carry fitness costs. As a result, aggressive behaviors vary significantly across animals and are likely acted on by natural selection to produce this variation. Aggression, and associated traits like nestmate discrimination, both complex traits, have well studied genetic components, with links to genes involved in processes like neuronal function, metabolism, and hormone and cuticular hydrocarbon (CHC) production and reception. However, whether and how natural selection acts on these genes to produce variation across species is not fully understood. Using a comparative genomics approach, we analyzed natural selection in ants (Hymenoptera: Formicidae) with candidate genes previously linked to these traits. We find that aggression is associated with shifts in selection intensity, including positive selection on neurotransmitter receptors, and that ants with low levels of nestmate discrimination experience positive or relaxed selection on several CHC genes. Interestingly, we find that most candidate genes analyzed experience positive selection across ants, regardless of aggression level or discrimination ability. Our results shed new light on the means by which natural selection may act to produce variation in aggression across the ants.