Data from: Heterozygosity-fitness correlation at the major histocompatibility complex despite low variation in Alpine ibex (Capra ibex)

Crucial for the long-term survival of wild populations is their ability to fight diseases. Disease outbreaks can lead to severe population size reductions, which makes endangered and reintroduced species especially vulnerable. In vertebrates, the major histocompatibility complex (MHC) plays an important role in determining the immune response. Species which went through severe bottlenecks, often show very low levels of genetic diversity at the MHC. Due to the known link between the MHC and immune response, such species are expected to be at particular risk in case of disease outbreaks. However, so far, only few studies have shown that low MHC diversity is correlated with increased disease susceptibility in species after severe bottlenecks. We investigated genetic variation at the MHC and its correlations with disease resistance and other fitness related traits in Alpine ibex (Capra ibex), a wild goat species that underwent a strong bottleneck in the last century and that is known to have extremely low genetic variability, both genome-wide and at the MHC. We studied MHC variation in male ibex of Gran Paradiso National Park, the population used as source for all post-bottleneck reintroductions. We found that individual MHC heterozygosity (based on six microsatellites) was not correlated with genome-wide neutral heterozygosity. MHC heterozygosity, but not genome-wide heterozygosity, was positively correlated with resistance to infectious kerato-conjunctivitis and with body mass. Our results show that genetic variation at the MHC plays an important role in disease resistance and, hence, should be taken into account for successfully managing species conservation.

野生动物种群抵御疫病的能力，是其长期存续的关键保障。疫病暴发可导致种群规模大幅缩减，令濒危物种与再引入物种尤为脆弱。在脊椎动物中，主要组织相容性复合体（major histocompatibility complex, MHC）在免疫应答调控中发挥关键作用。经历过严重种群瓶颈的物种，其MHC区域的遗传多样性往往极低。鉴于MHC与免疫应答之间的已知关联，这类物种在疫病暴发时将面临更高风险。然而迄今为止，仅有少数研究证实，经历严重种群瓶颈后的物种，其MHC多样性低下与疫病易感性升高存在显著关联。本研究以阿尔卑斯羱羊（Capra ibex）为对象——该物种为野生山羊类群，在上世纪经历过剧烈种群瓶颈，且全基因组及MHC区域均存在极低水平的遗传变异——分析了其MHC区域的遗传变异，以及该变异与疫病抗性及其他适应性相关性状的关联。本研究的采样对象为大帕拉迪索国家公园内的雄性阿尔卑斯羱羊，该种群是所有瓶颈后再引入项目的核心种源种群。研究发现，个体MHC杂合度（基于6个微卫星标记计算）与全基因组中性杂合度并无相关性。MHC杂合度（而非全基因组杂合度）与传染性角膜结膜炎抗性及体质量呈显著正相关。本研究结果表明，MHC区域的遗传变异在疫病抗性中发挥关键作用，因此在开展物种保护管理工作时，应将MHC遗传变异纳入考量范畴。