Genetic polymorphism for chemical tags in leaf-cutting ants

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Although social groups most obviously exhibit cooperation, they are also often the scene of conflict. Unless group members are clones, their reproductive interests will differ and individuals may benefit by exploiting the cooperative efforts of other group members. Cheating is therefore predicted to arise in all non-clonal systems, but is not thought to occur in one of the classic examples of cooperation, the rearing of brood by social insects. Adult workers would benefit by preferentially rearing brood to which they are more related into reproductive queens rather than sterile workers. Although the chemical recognition tags (cuticular hydrocarbons) are well known to differ between colonies, they are not thought to differ between genotypes. Workers are thus believed to lack the necessary information to distinguish larvae genotypically and so are unable to act nepotistically when rearing brood. Only two studies have tested this prediction, however, with one finding genetic polymorphism for chemical tags and the other not. The project will test the prediction in a leaf-cutting ant system that facilitates the detection of genetic polymorphism and which has an intriguing genotypic variation in caste propensity, with certain 'royal' genotypes that tend to develop into queens. By comparing the chemical tags of both adults and larvae of different genotypes, the project will test the evolutionary theory that there is not the necessary genetic polymorphism for nepotism to occur. It will also compare the tags of royal and normal genotypes to determine if the former have any special tag that tells nursing workers that they are royalty.