牦牛生态类型的分类

Classification of ecological types of the Chinese yak

为进一步弄清中国牦牛的遗传资源及其类型划分,利用微卫星DNA、随机扩增多态性(RAPD)、扩增片断长度多态性(AFLP)等3种分子遗传标记技术研究了麦洼牦牛、九龙牦牛、大通牦牛和天祝白牦牛的分类;并结合作者对牦牛染色体和血液蛋白多态性的研究结果探讨了中国牦牛类群的分类。结果:①根据微卫星位点的等位基因频率进行聚类分析,表明麦洼牦牛和九龙牦牛的遗传距离最大(1.506),麦洼牦牛2个群体之间的遗传距离最小(1.062)。5个牦牛群体被聚为两大类,四川九龙牦牛单独成一大类,其他牦牛群体聚为一类。②根据RAPD和AFLP两种分子遗传标记的分析,表明天祝牦牛和大通牦牛的遗传距离最小(0.0336),九龙牦牛和天祝牦牛的遗传距离最大(0.0414),4个牦牛品种被聚为两大类,九龙牦牛品种聚为一类,其它3个牦牛品种聚为一类。大通牦牛和天祝白牦牛在较近的水平上首先聚为一类,然后在较远处与麦洼牦牛聚为一大类。③根据染色体特征和血液蛋白位点的基因频率进行聚类的结果与微卫星DNA、RAPD、AFLP的聚类结果相似。中国牦牛可分为以九龙牦牛和麦洼牦牛为代表的两个类群(型)。这与蔡立等将中国牦牛分为“青藏高原型”和“横断高山型”的结果是一致的。而与其他学者的分类结果有较大的差异。结合中国牦牛品种(群体)的地理分布、生态条件、育成史及其分化的实际情况,作者认为中国牦牛分为两个大的生态类型是合理的。

To investigate the genetic resources and to clarify the classification status of the Chinese yak, the Maiwa, Jiulong, Datong and Tianzhu White yak were intensively studied using microsatellite DNA, RAPD and AFLP DNA markers on the basis of our previous work on the chromosomes and blood protein polymorphisms. The overall results showed that ： （ 1 ） the genetic distance based on allelic frequencies at microsatellite loci between the Maiwa and Jiulong yak was the largest （ 1. 506） and as expected that two populations of the Maiwa yak had the smallest genetic distance （1.062）. The four yak breeds were clustered into two groups, the Jiulong yak alone in a group and the rest of three breeds in another; （2） the genetic distance between the Datong and Tianzhu White yak was the smallest （0.0336） while it was the largest between the Jiulong and Maiwa yak （0.0414） based on the data from RAPD and RFLP analysis. The four yak breeds again clustered into two groups with the Datong and Tianzhu White yak grouped together first followed by the Maiwa yak; （3） the chromosome and blood protein polymorphisms analysis arrived to a similar pattern of breed relationship. Therefore it was concluded that the Chinese yak can be considered as two typos with the Jiulong and Maiwa yak as their representatives, respectively. This conclusion is in concordance with the proposal by later professor Cai Li and his colleagues who classified the Chinese yak as two types of the ‘Qinghai-Tibetan Plateau yak＇ and the ‘Hengduan Mountain Alpine yak＇, but differs from other classifications proposed by others. Taking into account of the geographic distribution, ecological factors, history and development of the Chinese yak, we believe that this classification is reasonable.