The significance of intercolonial variation of cuticular hydrocarbons for inbreeding avoidance in ant sexuals

The reproductive biology of social Hymenoptera is characterized by lifelong sperm storage by queens and sperm limitation in males. Both sexes are therefore expected to be especially choosy about their mating partners. In particular, sexuals should avoid sibmating because of the resulting risk of producing sterile diploid male offspring. Colonies of the ant Leptothorax gredleri are specialists of patchy habitats and often live in subpopulations of fewer than a few dozen colonies with restricted gene flow between patches. Sexuals therefore have a high probability of mating with a related partner. Using gas chromatography and mass spectrometry, we found that the blend of cuticular hydrocarbons, which is generally thought to be important in nestmate recognition in social insects, was colony specific in both sexes. In principle, this might provide sexuals with a chemical cue for the avoidance of sibmating. When allowed to choose among equal numbers of mating partners from their own and another nest in flight cages, sexuals had only a weak although significant preference for mating with non-nestmates. Other characters might therefore be more important than relatedness in mate choice.