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

The taxonomically widespread nature of polyandry remains a puzzle. Much of the empirical work regarding the costs and benefits of multiple mating to females has, for obvious reasons, relied on species that are already highly polyandrous. However, this makes it difficult to separate the processes that maintain the current level of polyandry from the processes that facilitate its expression and initiated its evolution. Here we consider the costs and benefits of polyandry in Nasonia vitripennis, a species of 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 with virgin males. Conversely, mating multiply with previously mated males actually results in a fecundity cost. Sexual harassment may also represent a significant cost of reproduction. Harassment was, however, only costly during oviposition, resulting in reduced fecundity, longevity and disrupted sex allocation. Our results show that ecological changes, in our case associated with differences in the local mating structure in the laboratory can alter the costs and benefits of mating and harassment and potentially lead to shifts in mating patterns.

一妻多夫制（polyandry）在分类学上的广泛分布现象至今仍是一个未解之谜。鉴于显而易见的原因，此前针对雌性多次交配的成本与收益开展的大量实证研究，均以已被证实存在高度一妻多夫制的物种为研究对象。然而，这使得研究者难以将维持当前一妻多夫制水平的演化过程，与促成该性状表达并启动其演化的过程区分开来。本研究以丽蝇蛹集金小蜂（Nasonia vitripennis）为研究对象，该物种为寄生蜂类群，野外状态下主要为单雄交配（monandrous），但在实验室培养条件下可演化出一妻多夫制性状。通过一系列共六项实验，我们发现：雌性若与未交配的雄蜂多次交配，可直接获得繁殖力与寿命方面的收益。反之，若与已交配过的雄蜂多次交配，则会带来繁殖力方面的代价。性骚扰同样可能构成繁殖过程中的一项显著代价，但研究发现，仅在产卵阶段发生的性骚扰才会产生代价，具体表现为繁殖力下降、寿命缩短以及性分配模式被打乱。本研究结果表明，生态环境变化——在本研究中具体体现为实验室环境下局部交配结构的差异——可改变交配与性骚扰的成本与收益格局，并可能最终引发交配模式的转变。