Department of Community Ecology, Helmholtz Centre for Environmental Research-UFZ, Theodor-Lieser-Str 4, 06120 Halle/Saale, Germany.
Mol Ecol. 2009 Mar;18(5):769-81. doi: 10.1111/j.1365-294X.2008.04057.x.
Depletion of polymorphism at major histocompatibility complex (MHC) genes has been hypothesized to limit the ability of populations to respond to emerging pathogens, thus putting their survival at risk. As pathogens contribute substantially to the global amphibian decline, assessing patterns of MHC variation is important in devising conservation strategies. Here, we directly compare levels of MHC class II and neutral variation between multiple populations of the great crested newt (Triturus cristatus) from refugial (REF: Romania) and postglacial expansion (PGE: Germany, Poland and UK) areas. REF populations harboured high levels of adaptive variation (24 expressed alleles), exhibiting clear signatures of historical positive selection, which points to the overall importance of MHC class II variation in this species. On the other hand, PGE populations were extremely depauperate (two alleles) but nevertheless have survived for c. 10,000 years, since the postglacial expansion. Variation in putative MHC class II pseudogenes, microsatellites and allozymes also showed a significant southern richness-northern purity pattern. The populations in the postglacial expansion area thus provide the clearest example to date of the long-term survival of populations in which MHC variation, historically under positive selection, has been depleted.
主要组织相容性复合体 (MHC) 基因多态性的消耗被假设为限制了种群对新出现的病原体的反应能力，从而使它们的生存面临风险。由于病原体是全球两栖动物减少的主要原因，评估 MHC 变异模式对于制定保护策略非常重要。在这里，我们直接比较了来自避难所（REF：罗马尼亚）和后冰河时代扩张（PGE：德国、波兰和英国）地区的多种大蝾螈（Triturus cristatus）种群的 MHC 类 II 和中性变异水平。REF 种群具有高水平的适应性变异（24 个表达等位基因），表现出明显的历史正选择特征，这表明 MHC 类 II 变异在该物种中总体上很重要。另一方面，PGE 种群极为贫乏（两个等位基因），但自后冰河时代扩张以来已经存活了大约 10000 年。假定的 MHC 类 II 假基因、微卫星和同工酶的变异也显示出明显的南部丰富北部纯净的模式。因此，后冰河时代扩张地区的种群提供了迄今为止最清晰的例子，证明了 MHC 变异（历史上受到正选择）已经消耗的种群能够长期生存。
