Adult survival in migratory caribou is negatively associated with MHC functional diversity

The genes of the major histocompatibility complex (MHC) are involved in acquired, specific immunity in vertebrates. Yet, only a few studies have investigated the fitness consequences of MHC gene diversity in wild populations. Here, we looked at the association between annual survival and body mass and MHC-DRB exon 2 (MHC-DRB) genetic diversity, obtained from high-throughput sequencing, in two declining migratory caribou (Rangifer tarandus) herds. To disentangle the potential direct and general effects of MHC-DRB genetic diversity, we compared different indices of diversity that were either based on DNA-sequence variation or on physicochemical divergence of the translated peptides, covering a gradient of allelic to functional diversity. We found that i) body mass was not related to MHC-DRB diversity or genotype and that ii) adult survival probability was negatively associated with PAM distance, a corrected distance that considers the likelihood of each amino acid substitution to be accep...

主要组织相容性复合体 (major histocompatibility complex) 基因参与脊椎动物的获得性特异性免疫。然而，目前仅有少数研究探讨了野生种群中MHC基因多样性的适合度后果。本研究针对两个正在衰退的迁徙驯鹿 (*Rangifer tarandus*) 种群，基于高通量测序 (high-throughput sequencing) 获得的MHC-DRB外显子2 (MHC-DRB exon 2) 遗传多样性数据，分析了其与年度存活率及体质量之间的关联。为了厘清MHC-DRB遗传多样性潜在的直接效应与一般效应，我们比较了基于DNA序列变异的不同多样性指数，以及基于翻译肽段理化差异的多样性指数，覆盖了从等位基因多样性到功能多样性的梯度范围。研究结果显示：其一，体质量与MHC-DRB多样性或基因型并无关联；其二，成年个体的存活概率与PAM距离 (PAM distance) 呈负相关——PAM距离是一种校正后的距离，其考量了每种氨基酸替换被接受的可能性……