Maternal control of offspring sex and male morphology in the Otitesella fig wasps

Abstract

Models concerning the evolution of alternative mating tactics commonly assume that individuals determine their own strategies. Here we develop a computer-based ESS model that allows mothers, ovipositing in discrete patches, to choose both the sex and the male mating tactics (natal-patch mating or dispersing) of their offspring based only on how many other mothers have used the specific patch before them. Data for three species of nonpollinating fig wasps from the Otitesella genus agree quantitatively with the model's assumptions and predictions. This suggests that females respond to population densities at the level of individual figs. The alternative male tactics in the species we studied are probably a result of a conditional strategy exercised by the mother that laid them. In addition, as females were only allowed to lay one egg per patch, our results suggest a new mechanism that can skew population sex ratios towards a female bias.