GREENE, MICHAEL/J; UNIVERSITY OF COLORADO AT DENVER: THE ROLE OF CUTICULAR HYDROCARBON STRUCTURAL COMPLEXITY IN ANT RECOGNITION CUES
In social insects, suites of hydrocarbon molecules present on the cuticle, known as hydrocarbon profiles, act as multi-component recognition cues. Social insects can use variation in hydrocarbon profiles as recognition cues in order to recognize group membership of other individuals they interact with. Group membership may include colony-membership, species membership or, within colonies, task membership or reproductive status. Recognition responses vary according to context, although the recognition of a non-member of a colony is often met with aggression by members of the colony. Although growing evidence has shown that cuticular hydrocarbons are used as recognition cues, we know little about the mechanism by which they communicate group status. For example, is the relevant information of the cue present in the entire hydrocarbon profile, or only in specific pieces? I studied the species recognition response of two ant species, Linepithema humile and Aphaenogaster cockerelli, to examine what role structural complexity plays in ant recognition responses mediated by hydrocarbon recognition cues. A bioassay was employed that measured the species recognition response of the ants to heterospecific hydrocarbon profiles, isolated structural classes from the heterospecific hydrocarbon profile, mixtures of the heterospecific structural classes and controls. The data show that the ants responded to structural complexity, a feature of complex cuticular hydrocarbon mixtures, and not simply to specific compounds or to the number of hydrocarbons in a mixture in their species recognition response. A combination of at least two hydrocarbon structural classes was necessary to elicit a response, however no one class of hydrocarbons was more important than the others in eliciting a response. Structural complexity in hydrocarbon recognition cues appears to provide a chemical context for a recognition response
