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（mixed-mating strategies，即雌雄同体生物中自体受精与异交处于中间水平的交配模式）在动植物中较为常见，但自然界中自体受精（self-fertilization，简称自交）率差异如此之大的原因至今难以阐释。本研究以一种部分自体受精的鱼类——斑纹隐小鳉（Kryptolebias marmoratus）为模式生物，验证了寄生虫有助于维持混合交配策略这一假说。研究结果显示，野生种群中的异交后代相较于自交后代，具有更高的遗传多样性，且对多种寄生虫感染的抗性更强。鉴于斑纹隐小鳉的异交仅能通过雄性与雌雄同体的交配实现，本研究数据为雄全同株物种中雄性与雌雄同体共存的现象提供了解释——这类物种的雌雄同体无法进行种内异交。此外，本研究还提供了证据，证实寄生虫在自然动物种群中对维持混合交配策略具有推动作用。