The costs and benefits of multiple mating in a mostly monandrous wasp

Abstract

The taxonomically widespread nature of polyandry remains a puzzle. Much of the empirical work regarding the costs and benefitsof multiple mating to females has, for obvious reasons, relied on species that are already highly polyandrous. However, thismakes it difficult to separate the processes that maintain the current level of polyandry from the processes that facilitate itsexpression and initiated its evolution. Here we consider the costs and benefits of polyandry in Nasonia vitripennis, a speciesof parasitoid wasp that is “mostly monandrous” in the wild, but which evolves polyandry under laboratory culture conditions.In a series of six experiments, we show that females gain a direct fecundity and longevity benefit from mating multiply withvirgin males. Conversely, mating multiply with previously mated males actually results in a fecundity cost. Sexual harassment mayalso represent a significant cost of reproduction. Harassment was, however, only costly during oviposition, resulting in reducedfecundity, longevity, and disrupted sex allocation. Our results show that ecological changes, in our case associated with differencesin the local mating structure in the laboratory can alter the costs and benefits of mating and harassment and potentially lead toshifts in mating patterns.