Local mate competition modifies the costs of mating in a mostly monandrous parasitoid wasp

The costs and benefits of mating are frequently measured in order to understand why females mate multiply. However, to separate the factors that initiate the evolution of polyandry (from monandry) from the factors that maintain it, we must ascertain how the environment changes the economics of mating. Here we show how context-dependent costs of mating can lead to the evolution of polyandry in a species that is monandrous in the wild, the parasitoid wasp Nasonia vitripennis. We have previously shown that when females have insufficient time between mating and ovipositing, they appear unable to process sperm effectively and end up overproducing sons (i.e. laying unfertilised eggs, since Nasonia is in haplodiploid). This overproduction of sons is costly due to selection on sex allocation in this species. Although N. vitripennis is monandrous in the wild, polyandry evolves under laboratory culture despite this sex allocation cost. In this study we show why: when groups of females oviposit to...为阐明雌性多次交配的演化动因，学界常对交配的成本与收益开展量化分析。然而，若要区分驱动一妻多夫制（polyandry）从单雄交配制（monandry）演化的起始因子，与维持该性状的维持因子，则需厘清环境如何改变交配的经济学效应。本研究以野外仅发生单雄交配的寄生蜂（parasitoid wasp）丽蝇蛹集金小蜂（Nasonia vitripennis）为对象，揭示了情境依赖型交配成本如何推动一妻多夫制的演化。此前我们的研究已证实，当雌蜂在交配与产卵间的时长不足时，无法有效处理精子，最终会过量产生雄性后代——即产下未受精卵，因丽蝇蛹集金小蜂属于单倍二倍体（haplodiploid）物种。由于该物种存在性分配选择压力，过量产生雄性后代会带来演化成本。尽管野外的丽蝇蛹集金小蜂仅进行单雄交配，但在实验室培养条件下，即便存在上述性分配成本，一妻多夫制仍会发生演化。本研究即阐明其中缘由：当多只雌蜂共同产卵时……