Polyandrous females provide sons with more competitive sperm: support for the sexy-sperm hypothesis in the rattlebox moth (Utetheisa ornatrix)

Given the costs of multiple-mating, why has female polyandry evolved? Utetheisa ornatrix moths are well-suited for studying multiple mating in females because females are highly polyandrous over their lifespan, with each male mate transferring a substantial spermatophore with both genetic and non-genetic material. The accumulation of resources might explain the prevalence of polyandry in this species, but another, not mutually-exclusive, possibility is that females mate multiply to increase the probability that their sons will inherit more-competitive sperm. This latter “sexy-sperm” hypothesis posits that female multiple mating and male sperm competitiveness co-evolve via a Fisherian runaway process. We tested the sexy-sperm hypothesis by using competitive double matings to compare the sperm competition success of sons of polyandrous versus monandrous females. In accordance with sexy-sperm theory, we found that in 511 offspring across 17 families, the male whose polyandrous mother mated...

鉴于多次交配需付出演化代价，雌性多配行为（polyandry）究竟是如何演化而来的？艳丽拟灯蛾（Utetheisa ornatrix）是研究雌性多次交配行为的理想实验模型：该物种的雌性在整个生命周期中均表现出高度的多配性，每只成功交配的雄性都会传递包含遗传与非遗传物质的大型精包（spermatophore）。资源积累假说或可解释该物种中多配行为的普遍性，但另一种并非互斥的可能性是：雌性通过多次交配，提升其子代雄性继承到更具竞争力精子的概率。这一后提出的‘性感精子假说（sexy-sperm hypothesis）’认为，雌性多次交配与雄性精子竞争力会通过费舍尔失控过程（Fisherian runaway process）实现共同演化。本研究通过竞争性双重交配实验，对比了多配雌性与单配雌性（monandrous）所产雄性后代的精子竞争成功率，以此检验性感精子假说。依据性感精子理论，我们在涵盖17个家系的511只子代个体中发现，其母亲为多配个体的雄性...