The swamp type of the Asian water buffalo is assumed to have been domesticated by about 4000 years BP, following the introduction of rice cultivation. Previous localizations of the domestication site were based on mitochondrial DNA (mtDNA) variation within China, accounting only for the maternal lineage. We carried out a comprehensive sampling of China, Taiwan, Vietnam, Laos, Thailand, Nepal and Bangladesh and sequenced the mtDNA Cytochrome b gene and control region and the Y-chromosomal ZFY, SRY and DBY sequences. Swamp buffalo has a higher diversity of both maternal and paternal lineages than river buffalo, with also a remarkable contrast between a weak phylogeographic structure of river buffalo and a strong geographic differentiation of swamp buffalo. The highest diversity of the swamp buffalo maternal lineages was found in south China and north Indochina on both banks of the Mekong River, while the highest diversity in paternal lineages was in the China/Indochina border region. We propose that domestication in this region was later followed by introgressive capture of wild cows west of the Mekong. Migration to the north followed the Yangtze valley as well as a more eastern route, but also involved translocations of both cows and bulls over large distances with a minor influence of river buffaloes in recent decades. Bayesian analyses of various migration models also supported domestication in the China/Indochina border region. Coalescence analysis yielded consistent estimates for the expansion of the major swamp buffalo haplogroups with a credibility interval of 900 to 3900 years BP. The spatial differentiation of mtDNA and Y-chromosomal haplotype distributions indicates a lack of gene flow between established populations that is unprecedented in livestock.
Sixteen polymorphic primers screened from 100 random primers were selected to analyze the randomly amplified polymorphic DNA (RAPD) of 540 domesticated black goats (Capra hircas) from 9 different geographical populations in Sichuan Province of China. After the test, 170 entirely repeatable RAPD markers representing goat polymorphisms were obtained from the 16 polymorphic primers, the lengths of the markers ranging from 0.1 to 2.5 kb. The genetic distance among the black goat populations ranges from 0.1051 to 0.2978. The similarity coefficient (0.9002) between Jintang and Lezhi black goats was the highest in the 9 populations, followed by the coefficient (0.8953) between Jialing and Yinshan goats, while that between Jiangan and Huili goats was found to be the lowest (0.7424). The coefficient of differentiation among population genes (Gst) was 0.2766, indicating a comparatively low degree of differentiation among the black goat populations. A UPGMA dendrogram constructed from similarity coefficients showed that the two populations from Huili and Baiyu, which are found mostly on the Western Sichuan plateau and in mountainous areas, clustered together, and the other seven populations formed another group. It can also be clearly seen that the Huili and Baiyu populations are very special, and must have been closely related in the past, even though their link with the other populations is quite weak as a result of genetic communication. The results of the experiment offer some crucial scientific data useful for the breeding of black goats.
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