从细胞色素b基因全序列差异分析岩羊和矮岩羊的系统进化关系

矮岩羊的分类地位从它被发现后就一直存在着争议。本文测定了分别来自四川和青海的岩羊(Pseudois nayaur)和矮岩羊(Pseudois schaeferi)共7个个体的Cyt b基因全序列(1140bp)，结合山羊(Capra hircus)、北山羊(Capra ibex)、绵羊(Ovis aries)和盘羊(Ovis ammon)同源DNA序列进行比较，分析了碱基组成和变异情况以及核苷酸序列差异。用简约法和距离距阵法构建了分子系统树，得到了相同的拓扑结构。结果显示：岩羊和矮岩羊互为单系群，有着较山羊、北山羊、绵羊和盘羊间更近的亲缘关系，它们之间的序列差异(Cyt b＝3．2％)低于牛科不同种间的序列差异水平(8．3％-12．1％)，明显高于种内个体的序列差异，而处于牛科亚种的序列差异范围内。因此，推测矮岩羊与岩羊之间的差异可能已经达到了亚种的水平。它们的分歧时间为l-3百万年动物学报49(2)：198—204，2003]。

A molecular phylogeny of Bharal and dwarf blue sheep based on mitochondrial cytochrome b gene sequences

The phylogenetic relationship between the bharal or blue sheep ( Pseudois nayau r ) and dwarf blue sheep ( Pseudois nayaur schaeferi ) has been an open qu estion. Total DNA was extracted and sequenced from three dried skin samples of b haral and four dwarf blue sheep from Sichuan and Qinghai provinces in China. The complete sequences were deposited in the GenBank (accession numbers: AF473602- AF473608). Based on the complete Cyt b gene sequences (1 140 bp) obtaine d from t hese samples, the authors aligned them using the Clustal W software program. By comparing the Cyt b sequences of four other species Capra hircus, Capra ib ex, Ovis ammon, Ovis aries in the family Bovidae, the divergences and base sub stitut io ns among these sequences were analyzed with the MEGA software. Accordingly, the base composition of bharal and dwarf blue sheep showed the same characters as th e other bovidae members. The phylogenetic trees constructed by multiple methods (NJ and MP) supported the same topology, in which the monophyly of bharal and dw arf blue sheep was obviously demonstrated and the phylogenetic trees were in agreement with the tra ditional morphological data. Our molecular results show that the sequence diverg ence between bharal and dwarf blu e sheep is lower than that between other species in the family Bovidae. However, the differences surpassed the corresponding number within intraspecific individ uals and were in the range of sequence variation that typically distinguishes su bspecies. Together with these data, the authors propose that the dwarf blue shee p ( Pseudois nayaur schaeferi ) should be a subspecies of the bharal ( Pseudois nayaur ). In addition, the divergence time s bet ween clades was discussed in accordance to the Cyt b molecular clock, which esti mated an approximate divergence time between the bharal and dwarf blue sheep of 1-3 million years