Acclimation in ants: Interference of communication and waterproofing through cuticular hydrocarbons in a multifunctional trait

Abstract

1. Organismal traits may experience conflicting selection pressures if they fulfil different functions simultaneously. This can require trade-offs between functions or alternatively functional separation between elements of the trait.2. An important multifunctional trait in insects is the cuticular hydrocarbon (CHC) layer. CHCs cover the body of nearly all insects, protect against desiccation and serve as a communication signal. In social insects like ants, they provide cues for nestmate recognition. To maintain their waterproofing function, insects have to adjust CHC composition to current temperatures. These changes might affect information content and interfere with communication, which would be especially detrimental in social insects.3. Here, we studied how acclimation affects nestmate recognition in two sister species of the ant genus Lasius. Colony fragments were exposed to three climate regimes. We analysed behaviour towards same and differently acclimated conspecifics, and determined which CHCs were related to acclimatory changes, colony differences and inter-individual aggression.4. Differential acclimation led to higher aggression and chemical distances among former nestmates. We identified small CHC subsets, which only differed among colonies or among acclimation treatments. Moreover, few compounds sufficed to explain inter-individual aggression, suggesting that ants do not use the entire CHC profile for nestmate recognition and that colony identity is encoded in a redundant way. 5. Across individual CHCs, their contribution to colony differences and to differences among acclimatory treatments was negatively correlated, indicating that there is some degree of functional separation. However, CHC classes could not be clearly assigned to one or another function, indicating that the role of each CHC is idiosyncratic and may differ among species. Acclimatory effects and colony differences were more independent from each other in L. platythorax than in L. niger, indicating that functional separation can differ even among sister species.

Reference genome of the antLasius platythorax

“…Cuticular hydrocarbons play an important role in ant communication, particularly in recognition of nestmates, and in waterproofing and defense against pathogens (Lenoir et al 2009). L. platythorax cuticular hydrocarbons are characterised by a high abundance of dimethyl and trimethyl alkanes with relatively high chain lengths (mostly between C33 and C37), and so are longer than those of L. niger (Wittke, Baumgart, and Menzel 2022; Baumgart et al 2022).…”