Choosy males could help explaining androdioecy in a selfing fish

Androdioecy (the coexistence of males and hermaphrodites) is considered a transitional state derived from pure hermaphroditism or dioecy, but the processes selecting for this rare breeding system are unclear, particularly in animals. In androdioecious species, the proportion of males in relation to hermaphrodites is usually so reduced that it is not known whether there is scope for mate choice, particularly when simultaneous hermaphrodites can self-fertilize. We investigated the potential role of male mate choice in the persistence of androdioecy in animals using a self-fertilizing androdioecious fish (Kryptolebias marmoratus) as a model. Hermaphrodites preferred to associate with males but showed no preference based on genetic similarity. In contrast, males displayed a strong preference for genetically dissimilar hermaphrodites, based, apparently, on olfactory cues. We suggest that disassortative male mate choice could be a critical factor in stabilizing androdioecy in cases where high selfing rates are associated with inbreeding depression.

雄全同体繁育系统（androdioecy），即雄性与雌雄同体个体共存的繁育模式，被认为是由纯粹雌雄同体或雌雄异体繁育系统演化而来的过渡状态，但驱动这一稀有繁育系统被自然选择青睐的过程仍不明晰，在动物类群中尤其如此。在雄全同体物种中，雄性个体相对于雌雄同体个体的占比通常极低，以至于难以判断是否存在配偶选择的进化空间，尤其是当同步雌雄同体个体可进行自体受精时。本研究以一种可进行自体受精的雄全同体鱼类——斑纹隐小鳉（Kryptolebias marmoratus）为模式生物，探究了雄性配偶选择在动物类群雄全同体繁育系统维持中的潜在作用。结果表明，雌雄同体个体更偏好与雄性共处，但未表现出基于遗传相似性的配偶偏好；与之相反，雄性个体则对遗传异质性的雌雄同体个体展现出强烈偏好，这一选择似乎依赖嗅觉线索。我们认为，当高自体受精率与近交衰退相伴发生时，雄性的异配配偶选择可能是维持雄全同体繁育系统稳定的关键因子。