Data from: Female stick insects mate multiply to find compatible mates

Why females of many species mate multiply in the absence of direct benefits remains an open question in evolutionary ecology. Interacting and mating with multiple males can be costly to females in terms of time, resources, predation risk, and disease transmission. A number of indirect genetic benefits have been proposed to explain such behaviors, but the relative importance of these mechanisms in natural systems remains unclear. We tested for several direct and indirect benefits of polyandry in the walking stick Timema cristinae. We found no evidence of direct benefits with respect to longevity or fecundity. However, male × female genotypic interactions affected egg-hatching success and offspring production independent of relatedness, suggesting that mating with certain males benefits females and that the best male may differ for each female. Furthermore, multiply mated females biased paternity toward one or few males, and the extent of this bias was positively correlated to egg-hatching success. Our data, therefore, provide evidence for indirect benefits through compatibility effects in this species. By mating multiply, females may improve their chances of mating with a compatible male if compatibility cannot be assessed before mating. Such compatibility effects can explain the evolution and maintenance of polyandry in Timema and many other species.

在缺乏直接收益的情况下，为何诸多物种的雌性会进行多次交配，始终是进化生态学领域的未解难题。雌性与多只雄性互动并交配，会在时间、资源、捕食风险以及疾病传播等方面付出代价。学界已提出多种间接遗传收益假说以解释此类行为，但这些机制在自然系统中的相对重要性仍不明朗。我们以克里斯娜竹节虫（Timema cristinae）为研究对象，检验了一妻多夫制（polyandry）的多种直接与间接收益。研究发现，在寿命与繁殖力方面并未发现直接收益的相关证据。然而，雌雄基因型互作会影响卵孵化成功率与后代产量，且该效应与亲缘关系无关，这表明与特定雄性交配可使雌性获益，且对每只雌性而言，最优雄性个体存在差异。此外，经历多次交配的雌性会将父权偏向某一只或少数几只雄性，且这种父权偏向的程度与卵孵化成功率呈正相关。因此，本研究的数据为该物种通过相容性效应获得间接收益提供了证据。若交配前无法评估相容性，雌性通过多次交配可提升与相容性匹配雄性交配的概率。此类相容性效应可解释克里斯娜竹节虫及诸多其他物种中一妻多夫制的演化与维持机制。