Bet-hedging and the evolution of multiple mating

Two related bet-hedging hypotheses have been proposed to explain the evolution of multiple mating by females. The first examines fitness of females within a single type of environment, and predicts that multiple mating can increase fitness by reducing the probability that all of a female's eggs are fertilized by a poor-quality male. The second examines fitness across environments and predicts that females who mate multiple times reduce the probability that all of their eggs are fertilized by a male that is unsuited to the current environment. We tested whether multiple mating actually provides the fitness benefits predicted by bet-hedging models by comparing the geometric mean fitness across generations of half-sib versus full-sib families of the milkweed bug, Lygaeus kalmii, reared on three different host plants. The variance in mean fitness (egg-to-adult survivorship) was always lower for offspring in half-sib families than for offspring of full-sib families. This translated into an average increase in geometric mean fitness of 4.1% within environments and 1.3% among environments for offspring of multiple-mated versus once-mated parents. These fitness increases are sufficient to produce rapid replacement of a once-mating genotype by a multiple-mating genotype. We conclude that multiple mating by parents reduces variation in offspring fitness and increases geometric mean fitness. We suggest that bet-hedging hypotheses are viable explanations for at least some of the variation in mating frequency observed in insects.