Abstract: Yak is an important breeding resource in the Karakorum-Pamir Region, and there are few reports on the genetic diversity and phylogenetic evolution of yak in this region. In this study, the genetic diversity of mtDNA Cytb gene in yak in Karakoram-Pamir Region was analyzed. The results showed that the full length of mtDNA Cytb gene was 1 140 bp, and the average contents of T, C, A and G bases were 26.2%, 29.0%, 31.7%, and 13.1%, respectively, and the A+T base content (57.9%) was greater than C+G base content (42.1%), presence of base Basis bias; a total of 10 polymorphic loci with 5 haplotypes were detected, and only the transformed variant type was obtained; the average haplotype diversity, nucleotide difference, and nucleoside acid diversity were 0.599±0.001 23, 3.363 and 0.002 59, respectively. The results based on the construction of phylogenetic trees in the domestic yak population which indicated that the yak in the Karakoram-Pamir Region is closely related to the wild yak, and has a close relationship with the Bazhou yak; using the representative sequence of yak and bovine subfamily submitted by GenBank, the phylogenetic tree was constructed by the maximum likelihood method. The results showed that the yak was closely related to the American bison and had a close relationship with the common cattle.

Key words: Karakorum-Pamir Region, yak, mtDNA Cytb, genetic diversity, phylogenetic

摘要： 牦牛是喀喇昆仑-帕米尔地区重要的畜种资源，而关于该区域牦牛遗传多样性和系统进化的研究鲜有报道。对喀喇昆仑-帕米尔地区牦牛mtDNA Cytb基因进行遗传多样性分析，结果表明：mtDNA Cytb基因全长为1 140 bp，其中T、C、A和 G碱基的平均含量分别为26.2%、29.0%、31.7%、13.1%，其中A+T碱基含量（57.9%）大于C+G碱基的含量（42.1%），存在碱基的偏倚性；共检测出10个多态位点，5个单倍型，变异类型仅有转换；检测的平均单倍型多样性0.599±0.00123，平均核苷酸差异性3.363，平均核苷酸多样性0.002 59。基于国内牦牛群体构建系统发育树表明：喀喇昆仑-帕米尔地区牦牛与野牦牛亲缘关系较近，与巴州牦牛亲缘关系较远；利用GenBank已提交的牦牛和牛亚科代表物种序列，选用最大似然法构建系统发育树，结果表明牦牛与美洲野牛亲缘关系较近，与普通牛亲缘关系较远。

关键词: 喀喇昆仑-帕米尔地区, 牦牛, mtDNA Cytb, 遗传多样性, 系统进化