In many species, individuals prefer mates that are genetically dissimilar at the major histocompatibility complex (MHC), likely because it improves offspring resistance to pathogens. Here, we provide the first characterization of the MHC class II peptide binding region in bluegill (Lepomis macrochirus) and examine its effect on mating patterns. We captured female and male bluegill during spawning and sequenced these fish at the MHC. We found strong evidence that positive selection promotes genetic diversity at the MHC in bluegill, with a 5:2 ratio of non-synonymous to synonymous mutations. However, we found no evidence that the MHC led to disassortative mating between females and parental males. Extra-pair mating and the presence of specialized cuckolder males may have an important, albeit still unresolved, role in shaping mating patterns at the MHC in bluegill. The immune genes of the MHC allow individuals to recognize and respond to pathogens. High sequence diversity at the MHC is thought to enable individuals to recognize a wider range of pathogens. In many animals, individuals select mates that have dissimilar MHC sequences, which can improve the immune function of their offspring. We provide the first characterization of the MHC class II gene in bluegill sunfish and show that selection appears to be increasing sequence diversity at this gene. However, we found no evidence that the MHC shapes mating patterns in this species.

中文翻译：

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主要组织相容性复合体 II 类的相似性不影响蓝鳃鱼 (Lepomis macrochirus) 的交配模式

在许多物种中，个体更喜欢在主要组织相容性复合体 (MHC) 上基因不同的配偶，这可能是因为它提高了后代对病原体的抵抗力。在这里，我们提供了蓝鳃鱼 (Lepomis macrochirus) 中 MHC II 类肽结合区的首次表征，并检查了其对交配模式的影响。我们在产卵期间捕获了雌性和雄性蓝鳃鱼，并在 MHC 对这些鱼进行了测序。我们发现了强有力的证据，表明正选择促进了蓝鳃鱼 MHC 的遗传多样性，非同义突变与同义突变的比例为 5:2。然而，我们没有发现证据表明 MHC 导致雌性和父母雄性之间的不匹配交配。多对交配和专门戴绿帽子的雄性的存在可能有一个重要的，尽管仍未解决，在蓝鳃鱼的 MHC 形成交配模式中的作用。MHC 的免疫基因使个体能够识别病原体并对其作出反应。MHC 的高序列多样性被认为使个人能够识别更广泛的病原体。在许多动物中，个体选择具有不同 MHC 序列的配偶，这可以提高其后代的免疫功能。我们提供了蓝鳃太阳鱼中 MHC II 类基因的第一个特征，并表明选择似乎正在增加该基因的序列多样性。然而，我们没有发现证据表明 MHC 塑造了该物种的交配模式。个体选择具有不同 MHC 序列的配偶，这可以提高其后代的免疫功能。我们提供了蓝鳃太阳鱼中 MHC II 类基因的第一个特征，并表明选择似乎正在增加该基因的序列多样性。然而，我们没有发现证据表明 MHC 塑造了该物种的交配模式。个体选择具有不同 MHC 序列的配偶，这可以提高其后代的免疫功能。我们提供了蓝鳃太阳鱼中 MHC II 类基因的第一个特征，并表明选择似乎正在增加该基因的序列多样性。然而，我们没有发现证据表明 MHC 塑造了该物种的交配模式。