Material and genetic benefits of female multiple mating and polyandry

The maintenance of female polyandry has traditionally been attributed to the material (direct) benefits derived from male mating resources (e.g. nuptial gifts) accrued by multiple mating. However, genetic (indirect) benefits offer a more robust explanation since only polyandrous, not monandrous, females may gain both material benefits from multiple mating and genetic benefits from multiple sires. Discriminating between material and genetic benefits is essential when addressing the mechanism by which polyandry is adaptively maintained, but are difficult to disentangle because they affect fitness in similar ways. To test the hypothesis that genetic benefits maintain polyandry, we compared four components of fitness (longevity, fecundity, hatching success and survivorship) between monandrous and polyandrous females in the ground cricket, Allonemobius socius. We discovered that females derived nongenetic benefits from mating multiply, in that the magnitude of the nuptial gift was positively, associated with the number of eggs produced. However, polyandrous females had over a two-fold greater hatching success and a 43% greater offspring survivorship, leading to a significantly higher relative fitness than the monandrous strategy. These results were independent of the confounding effects of material benefits, implying that genetic contributions play a large role in the maintenance of polyandry and potentially in the antagonistic coevolutionary relationship between polyandry and male nuptial gifts. (C) 2002 Published by Elsevier Science Ltd.