Genetic differentiation and gene flow among six sheep breeds of Mongolian group in China

Abstract

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, small-tailed Han sheep, Hu sheep, Tan sheep, Ujumuqin sheep and Bayinbuluk sheep) were analyzed using seven microsatellites. The trees were constructed from diversity coefficient (DC) distances among the six sheep populations. The overall heterozygote deficit across all the populations (F_it) was between 0.167 (OarAE101) and 0.044 (MAF33). The overall significant deficit of heterozygote, because of inbreeding within breeds, (F_is) was between 0.089 (OarFCB304) and 0.005 (MAF33). The coefficient of genetic differentiation (F_st) was between 0.100 (OarAE101) and 0.022 (OarFCB48). It 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 differentiation level were very low among sheep breeds of the Mongolian Group in China. The average number of effective migrants exchanged per generation (Nem) ranged from 2.7369 (Tan sheep and Bayinbuluk sheep) to 44.3928 (Tong sheep and Hu sheep), and the mean value was 11.25213. Significantly positive relationships between the level of genetic differentiation and geographical distance and 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).

References

1. Bolstein D, White R L, Skolick M (1980). Construction of a genetic linkagemap in man using restriction fragment length polymorphisms. Animal Journal, 32: 314–331
2. Chu M X, Wang J Z, Wang A G, Li N, Fu J L (2002). Genetic polymorphismsof five microsatellite loci in small Tail Han Sheep. Acta Genetica Sinica, 29(6): 502–506 (in Chinese)
3. Crawford A M, Dodds K G, Ede A J (1995). An autosomal genetic linkage mapof the sheep genome. Genetics, 140: 703–724
4. Gen R Q, Chang H, Yang Z P (2002). Study on the genetic investigationand appearance character of Hu sheep. Journalof Yangzhou University (Agricultural and Life Science Edition), 23(3): 37–40 (in Chinese)
5. Jia B, Chen J, Zhao R Q, Luo Q J, Yan G Q, Chen J (2003). Microsatellite analysis of genetic diversity and phylogeneticrelationship of eight sheep breeds in Xinjiang. Acta Genetica Sinica, 30(9): 847–854 (in Chinese)
6. Lu S X, Chang H, Tsunoda K, Ren Z J, Sun W, Yang Z P, Ren X L, Chang G B (2005).The levels of genetic differentiation of Small TailedHan Sheep and Tan Sheep populations using structural loci. Agricultural Sciences in China, 38(9): 1890–1897 (in Chinese)
7. Nei M (1931). Estimation of average heterozygosity and genetic distancefrom a small number of individuals. Genetics, 16: 97–159
8. Qu R Z, Hou L, Lu H L, Li H Y (2004).The gene flow of population genetic structure. Hereditas (Beijing), 26(3): 377–382 (in Chinese)
9. Rousset F (1997). Genetic differentiation and estimation of gene flowfrom F-statistics under isolationby distance. Genetics, 145: 1219–1228
10. Saitou N, Nei M (1987). The neighbor-joiningmethod: a new method for reconstructing phylogenetic trees. Mol Bio Evol, 4: 406
11. Satkin M (1993). Isolation by distance in equilibrium and non-equilibriumpopulation. Evolution, 47: 262–279
12. Tian F G, Ma Z J, Chen Z H (2005).The molecular ecology and biodiversity. Journal of Southwest University for Nationalities(Natural Science Edition), 31(1): 115–120 (in Chinese)
13. Wright S (1931). Evolution in Mendelian population. Genetics, 16: 91–159
14. Wright S (1978). Evolution and the Genetics of Populations, Volume 4:Variability Within and Among Natural Populations. Chicago: University of ChicagoPress
15. Yang Y, Ma Y H, Lu S J, Zhang Y H (2004a). Genetic diversity in seven Chinese indigenous sheep breeds basedon microsatellite analysis. BiodiversityScience, 12(6): 586–593
16. Yang Z P, Chang H, Sun W, Geng R Q, Mao Y J (2003).The comparison ofstructural loci and microsatellite marker on genetic differentiationin sheep (goat) populations. Chinese Journalof Animal and Veterinary Sciences, 34(5): 427–433 (in Chinese)
17. Yang Z P, Chang H, Sun W, Geng R Q, Ren Z J, Mao Y J (2004b). Investigation on polymorphism of 7 sheep microsatellitemarkers in sheep (goat) populations. Journalof Northwest Sci Tech University of Agri and For (Nat Sci Ed), 32(12): 69–74 (in Chinese)
18. Zou J Z, Wang M N, Niu J F (1994). Ancient History of Husbandry andVeterinary in China. Beijing: Agricultural Science Press of China, 113–118 (in Chinese)