中文摘要：

利用7对微卫星引物对中国蒙系6个绵羊品种（同羊、小尾寒羊、湖羊、滩羊、乌珠穆沁羊和巴音布鲁克羊）的遗传分化、基因流、遗传分化程度与地理距离间的关系进行分析，并利用遗传距离构建系统树。结果表明：6个绵羊群体中，总群体近交系数Fit最高的位点为OarAE101（0．1670），最低的为MAF33（0．0440）；群体间分化系数Fst最高的位点为OarAE101（0．1000），最低的为OarFCB48（0．0220）；群体内近交系数Fis最高的位点为OarFCB304（0．0890），最低的为MAF33（0．0050）。Fst平均为3．9％，即由各群体内个体间的差异引起的遗传变异是96．1％，说明遗传变异绝大部分存在于品种内，品种间的遗传分化水平很低。6个绵羊群体每世代两群体间有效迁移个体数为2．7369（滩羊和巴音布鲁克羊）～44．3928（同羊和湖羊），平均为11．2521，均反映出品种间的基因流通畅。品种间的遗传差异与地理距离呈显著相关。初步推断我国蒙系绵羊品种间的遗传分化主要是自然选择（生境异质性）作用的结果。

英文摘要：

The level of genetic differentiation, gene flow, and the relationship between geographical distance and genetic differentiation among six sheep populations of Mongolian group in China （Tong sheep, Xiaoweihan sheep, Hu sheep, Tan sheep, Ujumuqin sheep and Bayinbuluk sheep） were analyzed using 7 microsatellites. The phylogenetic trees were constructed from DC distances among six sheep populations. The global heterozygote deficit across all populations （Fit） was between 0. 167 0 （OarAE101） and 0. 044 0 （MAF33）. The overall significant deficit of heterozygotes because of inbreeding within breeds （Fis） was between 0. 089 0 （OarFCB304） and 0. 005 0 （MAF33）. The coefficient of genetic differentiation （Fst） was between 0. 100 0 （OarAE101） and 0. 022 0 （OarFCB48）. It was indicated that 3.9% of the total genetic variation could be explained by breed differences and the remaining 96.1 % by differences among individuals for each population. This illustrated that most variations existed within breeds and genetic differentiations level were very low among sheep breeds of Mongolian Group in China. The average number of effective migrants exchanged per generation ranged from 2. 736 9 （Tan sheep and Bayinbuluk sheep） to 44. 392 8 （Tong sheep and Hu sheep）, and the mean value was 11. 252 1. Significantly positive relationships between the level of genetic differentiation and geographical distance, genetic distances were detected. It is concluded that genetic differentiation of sheep breeds of Mongolian group in China is mainly the result of natural selection （different living conditions）.