中国7个绵羊品种mtDNA D-loop区序列的系统发育与起源研究

Origin and Phylogenetics of Seven Chinese Sheep Breeds Based on D-loop Sequence

为探讨中国绵羊的起源、进化及遗传多样性,对新疆、内蒙古、西藏、云南、宁夏、山东等地区7个地方绵羊品种和1个外来品种共59个体的线粒体D-loop全序列进行了测序分析。7个地方绵羊群体的单倍型多样度(Hd)和核苷酸多样度(π)分别平均为0.9960和0.0306,表明我国地方绵羊品种的控制区遗传变异丰富。系统发育和网络进化分析均将中国绵羊分为3个明显的支系,揭示中国绵羊存在3个独立的母系起源;并发现欧洲摩佛仑羊与支系B聚在一起,表明摩佛仑羊与中国绵羊有较近的亲缘关系。对mtDNA D-loop的3个支系进行核苷酸不配对分布曲线分析和Fu’s中性检验,结果显示3个支系的分布曲线均呈单峰形,且中性检验差异显著,表明绵羊3个支系可能曾经历群体扩张。

To investigate the origin, evolution and genetic diversity of Chinese domestic sheep （ovis）, complete D-loop sequences of 59 individuals from 7 local breeds from Xinjiang, Inner Mongolia, Tibet, Yunnan, Ningxia and Shandong and 1 imported breed were sequenced. Haplotype diversity （Hd） and nucleotide diversity （n） among 7 Chinese sheep population were 0. 996 0 and 0. 030 6 averagely, which indicate genetic variance within control region of Chinese sheep is abundant. Neibour-joining tree was constructed based on 59 D-loop sequences from 8 domestic sheep populations together with previously published wild sheep sequences. It supports there are three distinct lineages （A, B and C） in Chinese sheep. Mouflon was clustered with lineage B, which showed that it had close relationship with Chinese sheep. Further median-joining network analysis also showed three lineages were determined in Chinese sheep. The result suggests that Chinese sheep derived from three independent maternal ancestors. Analysis of mismatch distribu- tion showed unimodal distribution of three lineages. And Fu＇s test of selective neutrality revealed that three lineages were in departure from the neutrality, which the difference were significant （P d0. 001）. It implies three lineages of Chinese sheep ever experienced population expansion possibly.