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The body surface of nearly all insects, including ants, is covered with a lipid layer that largely consists of cuticular hydrocarbons (CHC). They fulfil several functions, the two best-studied ones being communication and protection against water loss. CHC profiles are astonishingly diverse as even a single individual can possess more than 100 different hydrocarbon molecules. Species vastly differ in their CHC composition, but also within species, CHC profiles vary among individuals of different sex, caste, fertility, age, health state, etc. This variation has been intensely studied especially in eusocial insects like ants, where differences are likely to have a signalling function. However, with so many sources of variation in CHC profiles, it is easy to lose track of which factors are more important than others, which patterns can be generalised, and which are idiosyncratic. Thus, we need a deeper understanding of how precisely different factors influence CHC variation. In this review, we aim to provide an overview of what is known to date about fixed and plastic CHC variation and discuss sources of variation on the level of individuals, social insect colonies, populations, and species. We focus on abiotic and biotic environmental factors, social structure and the genetic background as sources of CHC variation. Finally, we discuss how variation can be adaptive and how it can be constrained by biophysical and biosynthetic mechanisms. Focusing on clearly defined CHC traits will help us to build a predictive framework to understand how CHC profiles are shaped by multiple selection pressures, to identify how different sources affect fixed and plastic CHC variation, and to determine the adaptive value of CHC traits.
Sprenger et al. (Wed,) studied this question.