Demographic bottlenecks erode genetic diversity and may increase endangered species' extinction risk via decreased fitness and adaptive potential. The genetic status of species is generally assessed using neutral markers, whose dynamic can differ from that of functional variation due to selection. The MHC is a multigene family described as the most important genetic component of the mammalian immune system, with broad implications in ecology and evolution. The genus Lynx includes four species differing immensely in demographic history and population size, which provides a suitable model to study the genetic consequences of demographic declines: the Iberian lynx being an extremely bottlenecked species and the three remaining ones representing common and widely distributed species. We compared variation in the most variable exon of the MHCI and MHCII-DRB locus among the four species of the Lynx genus.

Demographic bottlenecks erode genetic diversity and may increase endangered species' extinction risk via decreased fitness and adaptive potential. The genetic status of species is generally assessed using neutral markers, whose dynamic can differ from that of functional variation due to selection. The MHC is a multigene family described as the most important genetic component of the mammalian immune system, with broad implications in ecology and evolution. The genus Lynx includes four species differing immensely in demographic history and population size, which provides a suitable model to study the genetic consequences of demographic declines: the Iberian lynx being an extremely bottlenecked species and the three remaining ones representing common and widely distributed species. We compared variation in the most variable exon of the MHCI and MHCII-DRB locus among the four species of the Lynx genus. The Iberian lynx was characterised by lower number of MHC alleles than its sister species (the Eurasian lynx). However, it maintained most of the functional genetic variation at MHC loci present in the remaining and genetically healthier lynx species at all nucleotide, amino acid, and supertype levels. Species-wide functional genetic diversity can be maintained even in the face of severe population bottlenecks which caused devastating whole genome genetic erosion. This could be the consequence of divergent alleles being retained across paralogous loci, an outcome that, in the face of frequent gene conversion, may have been favoured by balancing selection.

种群瓶颈会侵蚀遗传多样性，并通过降低适合度与适应潜力，加剧濒危物种的灭绝风险。当前对物种遗传状态的评估通常依赖中性标记，但由于选择作用的存在，中性标记的动态变化与功能变异的动态往往存在差异。主要组织相容性复合体（Major Histocompatibility Complex, MHC）是一类多基因家族，被认为是哺乳动物免疫系统中最为关键的遗传组分，在生态学与进化研究中具有广泛意义。猞猁属（Lynx）包含四个物种，其种群历史与种群规模差异悬殊，为研究种群衰退的遗传效应提供了理想模型：伊比利亚猞猁是经历过极端种群瓶颈的物种，其余三个物种则为分布广泛的常见种群。本研究对猞猁属四个物种的MHCI与MHCII-DRB位点中变异度最高的外显子的变异情况进行了比较分析。结果显示，伊比利亚猞猁的MHC等位基因数量较其姊妹物种欧亚猞猁更低，但在核苷酸、氨基酸以及超型各个层面上，该物种均保留了其余遗传健康状况更佳的猞猁物种所具有的大部分MHC位点功能遗传变异。即便遭遇引发全基因组遗传严重侵蚀的极端种群瓶颈，物种整体的功能遗传多样性仍可得以保留。这一现象可能源于旁系同源位点间保留了分化的等位基因；在频繁发生基因转换的背景下，平衡选择或许对这一结果起到了促进作用。