Data from: Ecology can inform genetics: disassortative mating contributes to MHC polymorphism in Leach’s storm-petrels (Oceanodroma leucorhoa)

Studies of MHC-based mate choice in wild populations generally test hypotheses by assuming female choice and male-male competition, whether or not mate choice dynamics have been previously determined for the species under study. Here we examined mate choice patterns in a small burrow-nesting seabird, the Leach’s storm-petrel (Oceanodroma leucorhoa), using the Major Histocompatibility Complex (MHC). The life history and ecology of this species is extreme: both partners work together to fledge a single chick during the breeding season, a task that requires regularly traveling hundreds of kilometers to and from foraging grounds over a six to eight-week provisioning period. Using a five-year dataset unprecedented for this species (n=1027 adults and 925 chicks), we found a positive relationship between variation in female reproductive quality and heterozygosity at Ocle-DAB2, a MHC class IIB locus. Contrary to previous reports rejecting disassortative mating as a mechanism for maintaining genetic polymorphism in this species, here we show that males make significant disassortative mate choice decisions. Variability in female reproductive success suggests that the most common homozygous females (Ocle-DAB201 / Ocle-DAB201) may be physiologically disadvantaged and, therefore, less preferred as lifelong partners for choosy males. The results from this study support the role of mate choice in maintaining high levels of MHC variability in a wild seabird species, and highlights the need to incorporate a broader ecological framework and sufficient sample sizes into studies of MHC-based mating patterns in wild populations in general.

针对野生种群中基于主要组织相容性复合体（Major Histocompatibility Complex, MHC）的配偶选择研究，通常会在未明确所研究物种配偶选择动态的前提下，以雌性选择与雄性竞争为默认前提验证相关假说。本研究以一种小型洞穴筑巢海鸟——白腰叉尾海燕（Oceanodroma leucorhoa）为研究对象，借助MHC分析其配偶选择模式。该物种的生活史与生态特征极具特殊性：繁殖季中，雌雄双方需共同抚育1只雏鸟至离巢，在此为期6至8周的育雏投喂期内，它们需要往返数百公里前往觅食地觅食。本研究依托该物种此前未见的5年数据集（样本量包含1027只成鸟与925只雏鸟），发现雌性繁殖质量的变异与MHC II类B基因座Ocle-DAB2的杂合性呈正相关关系。与此前该物种研究中否定异型交配作为维持遗传多态性机制的结论相悖，本研究证实雄性会做出显著的异型择偶决策。雌性繁殖成功率的变异表明，最常见的纯合子雌性（Ocle-DAB201 / Ocle-DAB201）可能存在生理劣势，因此对于具有择偶偏好的雄性而言，这类雌性作为终身配偶的吸引力更低。本研究结果证实了配偶选择在维持野生海鸟种群MHC高多样性中的作用，同时也强调，总体而言，在野生种群的MHC择偶模式研究中，纳入更广泛的生态框架与足够的样本量十分必要。