Data from: Can MHC-assortative partner choice promote offspring diversity? A new combination of MHC-dependent behaviors among sexes in a highly successful invasive mammal

Sexual selection involving genetically disassortative mate choice is one of several evolutionary processes that can maintain or enhance population genetic variability. Examples of reproductive systems in which choosers (generally females) select mates depending on their major histocompatibility complex (MHC) genes have been reported for several vertebrate species. Notably, the role of MHC-dependent choice in non-mating contexts, but in other kinds of social interactions such as in the establishment of complex social systems, has not yet drawn significant scientific interest and is virtually absent from the literature. We have investigated male and female MHC-dependent choice in an invasive population of North American raccoons (Procyon lotor) in Germany. Both male and female raccoons rely on olfaction for individual recognition. Males have an unusually complex social system in which older individuals choose unrelated younger ones to form stable male coalitions that defend territories and a monopoly over females. We have confirmed that females perform MHC-disassortative mate choice, and that this behavior fosters genetic diversity of offspring. We have also observed that males build coalitions by choosing male partners depending on their MHC, but in an assortative manner. This is the first observation of antagonistic MHC-dependent behaviors among sexes. We show that this is the only combination of MHC-dependent partner choice that leads to outbreeding. In the case of introduced raccoons, such behaviors can act together to promote the invasive potential of the species by increasing its adaptive genetic divergence.

涉及遗传异型交配选择的性选择，是若干可维持或增强种群遗传变异的进化过程之一。已有多项针对脊椎动物物种的研究报道了此类交配系统：即选择者（通常为雌性）依据主要组织相容性复合体（major histocompatibility complex，MHC）基因筛选配偶。值得注意的是，MHC依赖型选择在非交配情境下，以及诸如复杂社会系统构建这类其他社会互动中所发挥的作用，尚未引起学界的广泛关注，相关研究文献几乎空白。我们针对德国境内的北美浣熊（Procyon lotor）入侵种群，开展了雌雄个体MHC依赖型选择的相关研究。雌雄浣熊均依靠嗅觉完成个体识别。雄性浣熊拥有极为复杂的社会系统：年长个体选择无亲缘关系的年轻个体，组建稳定的雄性联盟以保卫领地，并使联盟成员独占与雌性的交配权。本研究证实，雌性浣熊会进行MHC异型交配选择，且该行为可提升后代的遗传多样性。我们同时观察到，雄性个体在组建联盟时，会依据MHC筛选雄性伙伴，但采用同型选择策略。这是学界首次在不同性别间观测到拮抗的MHC依赖型行为。研究表明，这种兼具雌雄两性的MHC依赖型伴侣选择组合，是唯一能够实现远交的模式。对于该入侵浣熊种群而言，这类行为可协同发挥作用，通过提升适应性遗传分化，增强该物种的入侵潜力。