Data from: MHC variation reflects the bottleneck histories of New Zealand passerines

Most empirical evidence suggests that balancing selection does not counter the effects of genetic drift in shaping post-bottleneck MHC genetic diversity when population declines are severe or prolonged. However, few studies have been able to include data from historical specimens, or to compare populations/species with different bottleneck histories. In this study we examined MHC class II B and microsatellite diversity in four New Zealand passerine (songbird) species that experienced moderate to very severe declines. We compared diversity from historical samples (collected circa 1884-1938) to present day populations. Using a Bayesian framework, we found that the change in genetic diversity from historical to contemporary samples was affected by three main factors: 1) whether the data were based on MHC or microsatellite markers, 2) species (as a surrogate for bottleneck severity) and 3) whether the comparison between historical and contemporary samples was made using historical samples originating from the mainland or using historical samples originating from islands. The greatest losses in genetic diversity occurred for the most severely bottlenecked species, particularly between historical mainland and contemporary samples. Additionally, where loss of diversity occurred, the change was greater for MHC genes compared to microsatellite loci.现有多数实证证据表明，当种群衰退剧烈或持续时，平衡选择无法抵消遗传漂变对瓶颈后种群主要组织相容性复合体（Major Histocompatibility Complex, MHC）遗传多样性的塑造效应。然而，鲜有研究能够纳入历史标本数据，或是对具有不同瓶颈历史的种群或物种开展比较分析。本研究针对4种经历过中等至极严重种群衰退的新西兰雀形目（鸣禽）物种的MHC II B类基因与微卫星遗传多样性进行了检测。我们将采集于约1884年至1938年的历史样本的多样性数据，与当代种群的对应数据进行了对比。通过贝叶斯框架分析，我们发现从历史样本到当代样本的遗传多样性变化主要受三类核心因素影响：1）数据是否基于MHC标记或微卫星标记；2）物种类型（作为瓶颈严重程度的替代指标）；3）历史与当代样本的对比是否采用源自大陆的历史样本，抑或是源自岛屿的历史样本。遗传多样性损失最为显著的类群为受瓶颈效应影响最严重的物种，尤其是在历史大陆样本与当代样本的对比场景中。此外，在出现遗传多样性损失的类群中，MHC基因的多样性变化幅度大于微卫星位点。