Li Dan, Sun Keping, Zhao Yunjiao, Lin Aiqing, Li Shi, Jiang Yunlei, Feng Jiang
Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, China; College of Animal Science and Technology, Jilin Agricultural University, Changchun, China.
Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University , Changchun , China.
PeerJ. 2017 Jan 25;5:e2917. doi: 10.7717/peerj.2917. eCollection 2017.
Genetic diversity is one of the pillars of conservation biology research. High genetic diversity and abundant genetic variation in an organism may be suggestive of capacity to adapt to various environmental changes. The major histocompatibility complex (MHC) is known to be highly polymorphic and plays an important role in immune function. It is also considered an ideal model system to investigate genetic diversity in wildlife populations. The Rufous-backed Bunting () is an endangered species that has experienced a sharp decline in both population and habitat size. Many historically significant populations are no longer present in previously populated regions, with only three breeding populations present in Inner Mongolia (i.e., the Aolunhua, Gahaitu and Lubei557 populations). Efforts focused on facilitating the conservation of the Rufous-backed Bunting () are becoming increasingly important. However, the genetic diversity of has not been investigated. In the present study, polymorphism in exon 2 of the MHCIIB of was investigated. This polymorphism was subsequently compared with a related species, the Meadow Bunting (). A total of 1.59 alleles/individual were detected in and 1.73 alleles/individual were identified in . . The maximum number of alleles per individual from the three populations suggest the existence of at least three functional loci, while the maximum number of alleles per individual from the three populations suggest the presence of at least four functional loci. Two of the alleles were shared between the and . Among the 12 unique alleles identified in , 10.17 segregating sites per allele were detected, and the nucleotide diversity was 0.1865. Among the 17 unique alleles identified in , eight segregating sites per allele were detected, and the nucleotide diversity was 0.1667. Overall, compared to other passerine birds, a relatively low level of MHC polymorphism was revealed in , which was similar to that in . Positive selection was detected by PAML/SLAC/FEL analyses in the region encoding the peptide-binding region in both species, and no recombination was detected. Phylogenetic analysis showed that the alleles from and belong to the same clade and the two species shared similar alleles, suggesting the occurrence of a trans-species polymorphism between the two species.
遗传多样性是保护生物学研究的支柱之一。生物体中高遗传多样性和丰富的遗传变异可能表明其具有适应各种环境变化的能力。主要组织相容性复合体（MHC）具有高度多态性，在免疫功能中发挥重要作用。它也被认为是研究野生动物种群遗传多样性的理想模型系统。栗斑腹鹀（Emberiza jankowskii）是一种濒危物种，其种群数量和栖息地面积都急剧下降。许多具有历史意义的种群在以前有人居住的地区已不复存在，目前仅在内蒙古存在三个繁殖种群（即敖鲁古雅、嘎海图和鲁北557种群）。致力于促进栗斑腹鹀（Emberiza jankowskii）保护的工作变得越来越重要。然而，尚未对栗斑腹鹀（Emberiza jankowskii）的遗传多样性进行研究。在本研究中，对栗斑腹鹀（Emberiza jankowskii）MHCIIB外显子2的多态性进行了研究。随后将这种多态性与相关物种——圃鹀（Emberiza cioides）进行了比较。在栗斑腹鹀（Emberiza jankowskii）中检测到每个个体有1.59个等位基因，在圃鹀（Emberiza cioides）中鉴定出每个个体有1.73个等位基因。栗斑腹鹀（Emberiza jankowskii）三个种群中每个个体的等位基因最大数量表明至少存在三个功能位点，而圃鹀（Emberiza cioides）三个种群中每个个体的等位基因最大数量表明至少存在四个功能位点。栗斑腹鹀（Emberiza jankowskii）和圃鹀（Emberiza cioides）之间共有两个等位基因。在栗斑腹鹀（Emberiza jankowskii）中鉴定出的12个独特等位基因中，每个等位基因检测到10.17个分离位点，核苷酸多样性为0.1865。在圃鹀（Emberiza cioides）中鉴定出的17个独特等位基因中，每个等位基因检测到8个分离位点，核苷酸多样性为0.1667。总体而言，与其他雀形目鸟类相比，栗斑腹鹀（Emberiza jankowskii）的MHC多态性水平相对较低，与圃鹀（Emberiza cioides）相似。通过PAML/SLAC/FEL分析在两个物种编码肽结合区的区域检测到正选择，未检测到重组。系统发育分析表明，栗斑腹鹀（Emberiza jankowskii）和圃鹀（Emberiza cioides）的等位基因属于同一进化枝，两个物种共享相似的等位基因，表明这两个栗斑腹鹀属物种之间发生了跨物种多态性。
