Postmating Sexual Selection Favors Males That Sire Offspring with Low Fitness

Abstract

Two's a Crowd The process by which males and females compete to maximize their individual fitness also affects the fitness of their offspring. Sexual selection largely results from polyandry (multiple mating by females), and several competing hypotheses attempt to explain the evolution of polyandry. Bilde et al. (p. 1705 ) staged double mating experiments in seed beetles to distinguish between the theories underlying cryptic female choice and sexual antagonism. Contrary to expectation, males of high genetic quality, as measured on the basis of the number of offspring sired when singly mated to a female, consistently produced fewer offspring when females were doubly mated to males of both high and low genetic quality. Thus, postmating sexual selection can favor male genotypes with low fitness, and females risk genetic costs when mating with multiple males.