Cuticular hydrocarbon evolution in parabiotic nest-sharing ants

Cuticular hydrocarbons (CHCs) are important for communication amongst insects, especially ants. Ants typically acquire a common set of CHC cues, a gestalt odor, when sharing a nest. However, this process is not well-understood in nests shared by several species. We investigated the cuticular hydrocarbon profiles of three species living within a single nest: the parabiotic ants Camponotus femoratus, Crematogaster levior, and a third lestobiotic Solenopsis species. We looked at hydrocarbon profiles of ants of different castes, including queens, males and both minor and major workers. We also compared the Cr. levior profiles to other Crematogaster species who were nesting solitarily. The two parabiotic ants Ca. femoratus and Cr. levior shared few CHC cues, although the reproductive castes of these species had significantly more interspecific overlap in cues than the workers. In contrast, the lestobiotic Solenopsis ants acquired cues from both species of ants with whom they shared nests. These findings suggest that the lestobiotic Solenopsis follows a more typical gestalt acquisition of cues, while the parabiotic worker ants do not form an interspecific gestalt odor. All of the solitary and parabiotic Crematogaster ants had hydrocarbons of similar chain-length. However, parabiotic Camponotus have longer hydrocarbons than their solitary congeners. Given the caste and worker differences in chemical similarity, we suggest parabiotic ants may face CHC-related informational constraints, especially amongst worker ants. This may be mediated by nestmate recognition processes. We hypothesize these parabiotic ants may provide an avenue for investigating non-reproductive chemical character displacement, with the selection on hydrocarbon traits being more pronounced amongst Campontous ants.