PARTITIONING OF REPRODUCTION IN MOTHER-DAUGHTER VERSUS SIBLING ASSOCIATIONS - A TEST OF OPTIMAL SKEW THEORY

A critical feature of cooperative animal societies is the reproductive skew, a shorthand term for the degree to which a dominant individual monopolizes overall reproduction in the group. Our theoretical analysi s of the evolutionarily stable skew in matrifilial (i.e., mother-daugh ter) societies, in which relatednesses to offspring are asymmetrical, predicts that reproductive skews in such societies should tend to be g reater than those of semisocial societies (i.e., societies composed of individuals of the same generation, such as siblings), in which relat ednesses to offspring are symmetrical. Quantitative data on reproducti ve skews in semisocial and matrifilial associations within the same sp ecies for 17 eusocial Hymenoptera support this prediction. Likewise, a survey of reproductive partitioning within 20 vertebrate societies de monstrates that complete reproductive monopoly is more likely to occur in matrifilial than in semisocial societies, also as predicted by the optimal skew model.