Data from: MHC class II diversity of koala (Phascolarctos cinereus) populations across their range

Major histocompatibility complex class II (MHCII) genes code for proteins that bind and present antigenic peptides and trigger the adaptive immune response. We present a broad geographical study of MHCII DA β1 (DAB) and DB β1 (DBB) variants of the koala (Phascolarctos cinereus) (n = 191) from twelve populations across eastern Australia, with a total of 13 DAB and 7 DBB variants found. We identified greater MHCII variation and, possibly, additional gene copies in koala populations in the north (Queensland and New South Wales) relative to the south (Victoria), confirmed by STRUCTURE analyses and genetic differentiation using analysis of molecular variance. The higher MHCII diversity in the north relative to south could potentially be attributed to (i) significant founder effect in Victorian populations linked to historical translocation of bottlenecked koala populations, and (ii) increased pathogen- driven balancing selection and/ or local genetic drift in the north. Low MHCII genetic diversity in koalas from the south could reduce their potential response to disease, although the three DAB variants found in the south had substantial sequence divergence between variants. This study assessing MHCII diversity in the koala with historical translocations in some populations contributes to understanding the effects of population translocations on functional genetic diversity.

主要组织相容性复合体II类（Major histocompatibility complex class II，MHCII）基因编码能够结合并呈递抗原肽、触发适应性免疫应答的蛋白质。本研究针对澳大利亚东部12个种群的考拉（Phascolarctos cinereus，样本量n=191）开展了大范围地理分布层面的MHCII DA β1（DAB）与DB β1（DBB）变异体研究，共检出13种DAB变异体与7种DBB变异体。相较于南部（维多利亚州）种群，北部（昆士兰州与新南威尔士州）的考拉种群具有更高的MHCII变异水平，且可能存在额外的基因拷贝，该结论经STRUCTURE群体结构分析与分子方差分析得到验证。北部种群更高的MHCII多样性可归因于以下两点：一是维多利亚州种群存在显著的奠基者效应，这与历史上对瓶颈化考拉种群的人为易位事件相关；二是北部种群受病原体驱动的平衡选择作用增强，或存在更显著的局部遗传漂变，或二者兼具。尽管南部种群检出的3种DAB变异体之间存在显著的序列差异，但南部考拉种群较低的MHCII遗传多样性可能会降低其应对疫病的潜在能力。本研究针对部分经历过历史种群易位的考拉开展MHCII多样性分析，有助于深入理解种群易位对功能遗传多样性的影响。