Data from: Mating portfolios: bet-hedging, sexual selection and female multiple mating

Polyandry (female multiple mating) has profound evolutionary and ecological implications. Despite considerable work devoted to understanding why females mate multiply, we currently lack convincing empirical evidence to explain the adaptive value of polyandry. Here, we provide a direct test of the controversial idea that bet-hedging functions as a risk-spreading strategy that yields multi-generational fitness benefits to polyandrous females. Unfortunately, testing this hypothesis is far from trivial, and the empirical comparison of the across-generations fitness payoffs of a polyandrous (bet hedger) versus a monandrous (non-bet hedger) strategy has never been accomplished because of numerous experimental constraints presented by most ‘model’ species. In this study, we take advantage of the extraordinary tractability and versatility of a marine broadcast spawning invertebrate to overcome these challenges. We are able to simulate multi-generational (geometric mean) fitness among individual females assigned simultaneously to a polyandrous and monandrous mating strategy. Our approaches, which separate and account for the effects of sexual selection and pure bet-hedging scenarios, reveal that bet-hedging, in addition to sexual selection, can enhance evolutionary fitness in multiply mated females. In addition to offering a tractable experimental approach for addressing bet-hedging theory, our study provides key insights into the evolutionary ecology of sexual interactions.一妻多夫制（polyandry，即雌性多次交配）具有深远的进化与生态影响。尽管学界已开展大量研究以解析雌性多次交配的动因，但目前我们仍缺乏令人信服的实证证据来阐释一妻多夫制的适应价值。本研究针对一项颇具争议的假说展开直接检验：风险分摊策略（bet-hedging）作为一种风险分散手段，可为一妻多夫雌性带来多代际的适合度收益。遗憾的是，对该假说的检验绝非易事；由于多数“模式生物”存在诸多实验限制，此前从未有人能够对一妻多夫（风险分摊者）与单夫制（非风险分摊者）两种交配策略的跨代际适合度收益进行实证比较。本研究借助体外受精（broadcast spawning）海洋无脊椎动物极强的可操作性与通用性，攻克了上述实验难题。我们能够针对同时分配至一妻多夫与单夫制交配策略的雌性个体，模拟其多代际的几何平均适合度。我们的实验方案分离并控制了性选择与纯风险分摊场景的效应，结果显示：除性选择之外，风险分摊策略还可提升多次交配雌性的进化适合度。本研究不仅为检验风险分摊理论提供了一套易于操作的实验方法，还为性互动的进化生态学研究提供了关键见解。