Data from: MHC variability in an isolated wolf population in Italy

Small, isolated populations may experience increased extinction risk due to reduced genetic variability at important functional genes, thus decreasing the population’s adaptive potential. The major histocompatibility complex (MHC), a key immunological gene cluster, usually shows high variability maintained by positive or balancing selection in response to challenges by pathogens. Here we investigated for the first time, the variability of 3 MHC class II genes (DRB1, DQA1, and DQB1) in 94 samples collected from Italian wolves. The Italian wolf population has been long isolated south of the Alps and is presently recovering from a recent bottleneck that decreased the population to less than 100 individuals. Despite the bottleneck, Italian wolves show remarkable MHC variability with 6–9 alleles per locus, including 2 recently described alleles at DRB1. MHC sequences show signatures of historical selective pressures (high d N/d S ratio, ω > 1.74) but no evidence of ongoing selection. Variation at the MHC genes and 12 background microsatellite loci were not apparently affected by the recent bottleneck. Although MHC alleles of domestic dog origin were detected in 8 genetically admixed individuals, these alleles were rare or absent in nonadmixed wolves. Thus, despite known hybridization events between domestic dogs and Italian wolves, the Italian wolf population does not appear affected by deep introgression of domestic dog MHC alleles.

小型孤立种群因重要功能基因的遗传多样性降低，灭绝风险可能升高，进而削弱种群的适应性演化潜力。主要组织相容性复合体（major histocompatibility complex, MHC）作为一类关键的免疫基因簇，通常通过应对病原体侵染的正向选择或平衡选择维持较高的遗传多样性。本研究首次针对94份意大利狼样本中的3个MHC II类基因（DRB1、DQA1与DQB1）的遗传多样性开展分析。意大利狼种群长期隔离于阿尔卑斯山以南，目前正从近期的种群瓶颈事件中恢复——该事件曾将种群规模缩减至不足100只。尽管经历了该种群瓶颈，意大利狼仍表现出显著的MHC多样性：每个基因座拥有6至9个等位基因，其中包括DRB1基因座上2个新近被报道的等位基因。MHC序列呈现出历史选择压力的特征（高非同义替换与同义替换比值，即dN/dS，ω>1.74），但未检测到当前持续存在的选择信号。MHC基因与12个背景微卫星基因座的遗传变异，似乎未受近期种群瓶颈效应的显著影响。尽管在8个遗传混杂的个体中检测到了家犬来源的MHC等位基因，但这类等位基因在非混杂的意大利狼中极为罕见或完全缺失。综上，尽管已知家犬与意大利狼存在自然杂交事件，但意大利狼种群似乎并未受到家犬MHC等位基因深度渐渗的影响。