Data from: Polyandrous females found fitter populations

Multiple mating by females (polyandry) requires an evolutionary explanation, because it carries fitness costs in many species. When mated females disperse alone to a new habitat, their offspring may have no option but to mate with their siblings and incur inbreeding depression. However, some of the offspring of polyandrous females may only be half siblings, reducing inbreeding depression when isolated groups of siblings only have each other as mates. We investigated this putative benefit of polyandry over monandry by initiating multiple genetically isolated populations of Callosobruchus maculatus beetles, each founded by a single female, who received a complete ejaculate from either one or two males. The early generations had comparable fitness, but the F4 and F5 descendants of doubly inseminated females were more numerous and had higher egg-to-adult survival than the descendants of singly inseminated females. This fitness benefit was of similar magnitude whether beetles were reared on their standard food plant, or on a less favourable food source. Our results suggest that polyandrous females produce fitter descendants in inbred founder populations and therefore that polyandry may affect movement ecology and invasion biology.雌性多次交配（一妻多夫，polyandry）需要进化层面的解释，因为在诸多物种中，该行为会带来适合度成本。当已交配的雌性独自扩散至新栖息地时，其后代别无选择，只能与同胞交配，进而引发近交衰退。然而，实行一妻多夫的雌性所产的部分后代仅为半同胞，当孤立的同胞群体只能以彼此为交配对象时，这一情况可减轻近交衰退程度。本研究针对一妻多夫相较于单配偶制（monandry）的这一假定益处展开探究：我们构建了多个遗传隔离的绿豆象（Callosobruchus maculatus）种群，每个种群均以单头雌性作为奠基个体创立，该雌性分别接受1头或2头雄性的完整精液。早期世代的适合度水平相当，但两次交配雌性的F4、F5代后代数量更多，且卵至成虫存活率高于单次交配雌性的后代。无论绿豆象被饲养在标准寄主植物还是较不适宜的食物源上，该适合度益处的强度均相近。本研究结果表明，在近交奠基种群中，实行一妻多夫的雌性能够产生适合度更高的后代，因此一妻多夫行为可能会对扩散生态学与入侵生物学产生影响。