Data from: Best of both worlds? Association between outcrossing and parasite loads in a selfing fish

Mixed-mating strategies (i.e. intermediate levels of self-fertilization and outcrossing in hermaphrodites) are relatively common in plants and animals, but why self-fertilization (selfing) rates vary so much in nature has proved difficult to explain. We tested the hypothesis that parasites help maintain mixed-mating using a partially selfing fish (Kryptolebias marmoratus) as a model. We show that outcrossed progeny in the wild are genetically more diverse and less susceptible to multiple parasite infections than their selfed counterparts. Given that outcrossing in K. marmoratus can only be attained by male-hermaphrodite matings, our data provides an explanation for the coexistence of males and hermaphrodites in androdioecious species where hermaphrodites are unable to outcross among themselves. Moreover, our study provides evidence that parasites contribute to maintaining mixed-mating in a natural animal population.

混合交配策略（即雌雄同体兼具中等水平的自交与异交）在动植物中较为普遍，但自然界中自交率差异悬殊的成因始终难以阐释。我们以部分自交的斑纹隐小鳉（Kryptolebias marmoratus）为实验模型，验证了寄生虫可助力维持混合交配策略的假说。研究结果显示，野生种群中的异交后代遗传多样性更高，且相较于自交后代，对多种寄生虫感染的易感性更低。鉴于斑纹隐小鳉的异交仅能通过雄体与雌雄同体的交配完成，我们的数据为雄全同株物种中雄体与雌雄同体的共存现象提供了合理解释——这类物种的雌雄同体个体之间无法实现异交。此外，本研究还提供了证据，表明寄生虫在自然动物种群中对混合交配策略的维持具有积极贡献。