Data from: Mhc-linked survival and lifetime reproductive success in a wild population of great tits

Major histocompatibility complex (Mhc) genes are frequently used as a model for adaptive genetic diversity. Although associations between Mhc and disease resistance are frequently documented, little is known about the fitness consequences of Mhc variation in wild populations. Further, most work to date has involved testing associations between Mhc genotypes and fitness components. However, the functional diversity of the Mhc, and hence the mechanism by which selection on Mhc acts, depends on how genotypes map to the functional properties of Mhc molecules. Here, we test three hypotheses that relate Mhc diversity to fitness: (1) the maximal diversity hypothesis; (2) the optimal diversity hypothesis, and (3) effect of specific Mhc types. We combine mark-recapture methods with analysis of long-term breeding data to investigate the effects of Mhc class I functional diversity (Mhc supertypes) on individual fitness in a wild great tit (Parus major) population. We found that the presence of three different Mhc supertypes was associated with three different components of individual fitness: survival, annual recruitment and lifetime reproductive success (LRS). Great tits possessing Mhc supertype 3 experienced higher survival rates than those that did not, whereas individuals with Mhc supertype 6 experienced higher LRS and were more likely to recruit offspring each year. Conversely, great tits that possessed Mhc supertype 5 had reduced LRS. We found no evidence for a selective advantage of Mhc diversity, either in terms of maximal or optimal supertype diversity. Our results support the suggestion that specific Mhc types are an important determinant of individual fitness.

主要组织相容性复合体（Major histocompatibility complex, Mhc）基因常被用作适应性遗传多样性的研究模型。尽管Mhc与抗病性之间的关联已被广泛报道，但目前对于野生种群中Mhc变异所带来的适合度后果仍知之甚少。此外，迄今为止的多数相关研究均聚焦于检验Mhc基因型与适合度组分之间的关联。然而，Mhc的功能多样性，以及Mhc所受选择发挥作用的机制，均取决于基因型如何映射至Mhc分子的功能属性。本研究针对三项关联Mhc多样性与适合度的假说展开检验：（1）最大多样性假说；（2）最优多样性假说；（3）特定Mhc型别的效应。我们结合标记重捕法（mark-recapture methods）与长期繁殖数据分析，探究了Mhc I类功能多样性（即Mhc超型，Mhc supertypes）对野生大山雀（Parus major）种群个体适合度的影响。研究结果显示，三种不同的Mhc超型分别与个体适合度的三个组分存在显著关联：存活率、年度补充率与终生繁殖成功率（LRS）。携带Mhc超型3的大山雀存活率显著高于未携带该超型的个体；而携带Mhc超型6的个体则拥有更高的终生繁殖成功率，且每年成功招募后代的概率更高。与之相反，携带Mhc超型5的大山雀终生繁殖成功率显著降低。我们未发现任何证据表明Mhc多样性（无论是最大超型多样性还是最优超型多样性）存在选择优势。本研究结果支持“特定Mhc型别是决定个体适合度的重要因素”这一学术观点。