峨眉树蛙配偶选择的进化机制

Why are males or females so choosy when it comes to mating? This question has puzzled and marveled evolutionary and behavioral ecologists for decades since Charles Darwin proposed the concept of sexual selection in 1871. Our recent work shows that the Omei treefrog (Rhacophorus omeimontis) has polyandrous mating systems. In such systems, females receive no resources from males except sperm, but females still express a preference among males, and males show significant variation in reproductive successs,which probably indicated that individual variation in reproductive success among males might arise from females preferring mates that are able to provide high genetic quality. Thus, in this project we will study individual variation in reproductive success among males, individual variation in fitness among offspring, and the relation between those variation and MHC genotypes of female and its mates in Omei treefrog using the methods of behaviour observation and molecular genetic analyses to test the hypothesis that females can increase the reproductive success and the fitness by mating only with males that will contribute rare MHC (major histocompatibility complex) alleles(good genes) and/or dissimilar MHC alleles (compatible genes) to their offspring. The prospective results will reveal the evolutionary mechanisms of mate choice in the Omei treefrog, and thus promote the development of good genes and compatible genes theories of mate choice in animal.

为什么雌性要选择特定的配偶来繁殖后代呢？这是自达尔文1871年提出性选择概念以来，进化生物学家和行为生态学家一直在回答，但至今仍未找到明确答案的问题。我们的研究发现：峨眉树蛙具有"一雌多雄制"的婚配制度，雄性除提供精子外，在繁殖时没有给予雌性任何直接利益，但它们的繁殖成功率依然存在较大的差异。这似乎暗示着峨眉树蛙的雌性对交配的雄性有所选择，雄性遗传质量的差异导致了它们繁殖成功率的差异。因此，我们拟利用行为观察和实验分析相结合的方法，研究峨眉树蛙：1）雄性繁殖成功率的差异；2）子代适合度的差异；以及3）前述二者与抱对雌雄个体MHC基因之间的关联性，验证"峨眉树蛙雌性选择具有MHC稀有等位基因（优质基因）和/或具有不相似MHC等位基因（相容性基因）的雄性配偶，将获得最大的繁殖成功率和后代适合度"的理论假设，揭示峨眉树蛙配偶选择的进化机制，进而促进动物配偶选择的优质基因和相容性基因理论的发展。

利用野外行为观察和实验分析相结合的方法，分析了峨眉树蛙雄性个体的繁殖成功率、子代的适合度，以及二者与抱对雌雄个体MHC基因兼容性之间的相关性，从而检测繁殖保障假说、优质基因假说、遗传相容性假说和遗传多样性假说。研究发现不同抱对位置以及参与不同繁殖次数的雄性峨眉树蛙间繁殖成功率均具有显著的差异，但与雌雄个体的亲缘关系、MHC基因兼容性之间没有显著的相关性；雌性峨眉树蛙对雄性没有选择性，在一雌多雄制的婚配制度中没有获得任何好处；而雄性在一雌多雄制的婚配制度中可以获得多次参加交配的机会，增加其繁殖成功率；雌性在繁殖过程中没有有效的手段和行为阻止多个雄性参加抱对和繁殖。因此，我们认为峨眉树蛙的雌性处于被动的位置，对雄性配偶没有选择性，雄性追求更大的繁殖适合度利益促成了峨眉树蛙一雌多雄制婚配制度的形成。