Abstract: The genetic diversities and population structures of Meriones meridianus representing 4 populations in the Qaidam Basin were investigated by examining mitochondrial Cyt b sequences. The results showed that Lenghu-Suganhu population had the highest genetic diversity (Hd =  1.000; π = 0.00530), while the Geermu population had the lowest(Hd = 0.750; π = 0.00255). AMOVA analyses indicated that 38.32% of the total genetic variation was attributable to differences among populations and 61.68% to differences among individuals within populations. A low level of genetic differentiation was found between the Lenghu-Suganhu and other populations and a high level was detected between the Geermu and other populations. Gene flow was extensive between populations except for the Geermu population. Phylogenetic analysis revealed that, as the original population in Qaidam Basin, M. meridianus in Lenghu-Suganhu spread from west to east along the basin periphery. The results of Mantel test illustrated that it was not obviously relevant between genetic distance and geographic distance among geographic populations (r = 0.031, P = 0.938). The Last Greatest Lakes Period on the Qinghai-Tibet Plateau might be the major cause for genetic differentiation among M. meridianus populations in the Qaidam Basin.

Key words: Cyt b, Environmental variation, Genetic diversity, Midday gerbil (Meriones meridianus), Phylogenetic evolution, Qaidam Basin

摘要： 对采集自柴达木盆地4个子午沙鼠种群的线粒体Cyt b部分序列进行测序，分析其遗传多样性和种群间系统进化关系。结果显示：冷湖—苏干湖种群的遗传多样性最高（Hd = 1.000；π = 0.00530），花土沟种群的遗传多样性最低（Hd = 0.750；π = 0.00255）。分子变异分析结果显示61.68%的变异来自种群内，38.32%的变异来自种群间。其中, 冷湖—苏干湖种群与其他种群之间的遗传分化水平相对较低，格尔木种群与其他种群之间有较高水平的遗传分化。系统进化分析显示柴达木盆地子午沙鼠以冷湖—苏干湖为发源地沿盆地周边自西向东扩散，各种群之间存在广泛的基因交流。由于地理阻隔，格尔木种群与其他种群间基因交流较少。各地理种群间遗传距离与地理距离不相关。青藏高原大湖期是柴达木盆地各种群之间产生遗传分化的主要原因。

关键词: 子午沙鼠, Cyt b, 柴达木盆地, 遗传多样性, 系统进化, 环境变化