Non-random behavioural interactions among genetic subgroups in a polygynous ant

Abstract

Abstract. Genetic variation within colonies of some species of ants is increased by polygyny, in which two or more queens contribute their own genetically distinct offspring to a single worker population. Consequently, a colony contains two or more genetic subgroups, and workers encounter highly related individuals as well as colony members from other familial lines. Colonies of Formica argentea, each containing two or three queens, were used to investigate the hypothesis that workers exhibit nepotism by directing preferential behaviour towards their own kin. Observations of grooming and feeding interactions among workers showed cases of preferential behaviour directed by workers towards not only individuals of their own genetic subgroup but also towards workers of different genetic subgroups. Thus, worker ants behaved non-randomly with respect to genetic subgroups. Preferential behaviour towards particular subgroups may have been a consequence of task specialization among the subgroups; a high frequency of interaction among workers was correlated with particular tasks performed by different subgroups. Furthermore, there was no apparent preference by individuals or genetic subgroups for particular queens; grooming and feeding behaviour were not directed towards mother-queens. Therefore, worker-worker and worker-queen interactions did not support a conclusion of nepotism.