Genetic studies have typically inferred the effects of human impact by documenting patterns of genetic differentiation and levels of genetic diversity among potentially isolated populations using selective neutral markers such as mitochondrial control region sequences, microsatellites or single nucleotide polymorphism (SNPs). However, evolutionary relevant and adaptive processes within and between populations can only be reflected by coding genes. In vertebrates, growing evidence suggests that genetic diversity is particularly important at the level of the major histocompatibility complex (MHC). MHC variants influence many important biological traits, including immune recognition, susceptibility to infectious and autoimmune diseases, individual odours, mating preferences, kin recognition, cooperation and pregnancy outcome. These diverse functions and characteristics place genes of the MHC among the best candidates for studies of mechanisms and significance of molecular adaptation in vertebrates. MHC variability is believed to be maintained by pathogen-driven selection, mediated either through heterozygote advantage or frequency-dependent selection. Up to now, most of our knowledge has derived from studies in humans or from model organisms under experimental, laboratory conditions. Empirical support for selective mechanisms in free-ranging animal populations in their natural environment is rare. In this review, I first introduce general information about the structure and function of MHC genes, as well as current hypotheses and concepts concerning the role of selection in the maintenance of MHC polymorphism. The evolutionary forces acting on the genetic diversity in coding and non-coding markers are compared. Then, I summarise empirical support for the functional importance of MHC variability in parasite resistance with emphasis on the evidence derived from free-ranging animal populations investigated in their natural habitat. Finally, I discuss the importance of adaptive genetic variability with respect to human impact and conservation, and implications for future studies.

中文翻译：

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免疫基因变异性（MHC）在进化生态学和保护中的重要性。

遗传研究通常通过使用选择性中性标记（例如线粒体控制区序列，微卫星或单核苷酸多态性（SNPs））记录潜在分离群体中的遗传分化模式和遗传多样性水平来推断人类影响。但是，种群内部和种群之间的进化相关和适应性过程只能通过编码基因来反映。在脊椎动物中，越来越多的证据表明，在主要组织相容性复合体（MHC）的水平上，遗传多样性尤其重要。MHC变体影响许多重要的生物学特征，包括免疫识别，对传染性和自身免疫性疾病的敏感性，个别气味，交配偏好，亲属识别，合作和妊娠结局。这些多样的功能和特性使MHC的基因成为研究脊椎动物分子适应机制和意义的最佳人选。据信，MHC变异性是由病原体驱动的选择维持的，通过杂合子优势或频率依赖性选择介导。到现在为止，我们的大多数知识都来自于人类的研究或来自实验，实验室条件下的模型生物的研究。在自然环境中自由放养的动物种群对选择性机制的经验支持很少。在这篇综述中，我首先介绍有关MHC基因结构和功能的一般信息，以及有关选择在维持MHC多态性中作用的最新假设和概念。比较了在编码和非编码标记中作用于遗传多样性的进化力。然后，我总结了对MHC变异性在寄生虫抗性中的功能重要性的经验支持，重点是从在自然栖息地调查的自由放养动物种群获得的证据。最后，我讨论了适应性遗传变异对于人类影响和保护的重要性，以及对未来研究的意义。