Analysis on genetic diversity and isolation mechanism by distance of different ecological type sheep breeds in Mongolia sheep group.

In the present study with Tan sheep, small-tailed Han sheep, Hu sheep, Tong sheep, and Wadi sheep, we detected the distribution of gene frequency of several microsatellite sites in different chromosomes, the result showed that: 1) Hu sheep was in the status of Hardy-Weinberg extreme disequilibrium (P < 0.01), while populations including Tong sheep, small-tailed Han sheep, Tan sheep, and Wadi sheep were in Hardy-Weinberg equilibrium (P > 0.05). 2) Variance analysis of the heterozygosity and polymorphic information content at microsatellite makers showed that there were not significant differences among populations as to heterozygosity and PIC (P > 0.05), as to effective number of alleles there were not significant differences both among Tan sheep, Hu sheep, Tong sheep, and Wadi sheep, and between Wadi sheep and small-tailed sheep (P > 0.05), but between the former three populations and the latter two populations, there were significant differences (0.01<P < 0.05). The variation levels of small-tailed Han sheep was the highest in the five populations based on microsatellite maker data, subsequently followed by Wadi sheep, Tong sheep, Tan sheep, and then Hu sheep. 3) The phylogenetic relationships of the five sheep populations in this study did not meet the mechanism of isolation by distance, and the genetic differentiation relationships among five sheep populations were not closely linearly correlative with their geography distribution. Our findings supported related records in literature:The five populations originated on different time stage from the primogenitor population and communicated genetically with each other thereafter in the process of natural and artificial selection and on different ecological environment.