Sex ratio conflicts, mating frequency, and queen fitness in the ant Formica truncorum

Abstract

We examined the effect of facultative sex allocation by workers on queen fitness in a Finnish population of the ant Formica truncorum. Workers rear female-biased broods in colonies headed by a singly mated queen and male-biased broods in colonies headed by a multiply mated queen. As a result, multiply mated queens have a 37% fitness advantage over singly mated queens. Neither reproductive output nor worker population of colonies varied with queen mating frequency. We suggest that singly mated queens persist in the population because fitness benefits to multiply mated queens via sex allocation are balanced by costs of additional matings. Alternatively, singly mated queens may persist simply because some queens lack opportunities to mate multiply or because male control sometimes prevents additional matings by queens.