基于线粒体细胞色素b基因的中国大沙鼠系统地理格局

通过内蒙、新疆、甘肃的41个大沙鼠样品和1个伊朗撒拉克大沙鼠的mtDNA Cytb基因全序列的遗传分析,对我国大沙鼠(Rhombomys opimus)的分子系统地理学进行了初步探讨。结果表明,我国41个大沙鼠样品的Cytb基因包含了50个核苷酸变异位点(占全序列的4.39%),其中转换48个,颠换2个,共定义23个单倍型。在四个地理种群中,内蒙古中部半荒漠区和阿拉善荒漠区的单倍型多样性最高,甘新荒漠区的单倍型多样性最低;北疆荒漠区的核苷酸多样性最高,内蒙古中部半荒漠区的核苷酸多样性最低。分子变异分析(AMOVA)表明,种群间的遗传变异占51.68%,种群内的遗传变异占48.32%。FST统计结果表明,除内蒙古中部半荒漠区与阿拉善荒漠区地理种群之间差异显著外(P<0.05),其它地理种群间的差异均极显著(P<0.01)。基于单倍型的系统树显示,42只大沙鼠形成三支。其中,伊朗撒拉克地区大沙鼠和中国地区大沙鼠之间的亲缘关系比中国两支大沙鼠之间的亲缘关系远;分析表明,中国分布的大沙鼠两支之间分歧时间估计在0.093Ma前。嵌套支分析表明,大沙鼠历史种群曾发生过异域片段化、受阻碍基因流和持续种群扩张事件。种群扩张分析提示大沙鼠在0.0119Ma前曾经历过一次种群扩张事件,种群可能受到末次冰期波动的影响。

Phylogeographic patterns of the great gerbil Rhombomys opimus in China based on mitochondrial cytochrome b gene sequence variations

To address the phylogeographic patterns of great gerbils(Rhombomys opimus)in the arid regions of China,we examined DNA sequence variations in the mitochondrial cytochrome b gene of the 41 individuals from Inner Mongolia,Xinjiang and Gansu,and one from Sarakhs,Iran in GenBank.We detected 50 nucleotide sites were variable(4.39% in the full sequences),including 48 transitions and 2 transversions among the 1 140 base pairs(bp)of the mitochondrial cytochrome b gene.A total of 23 haplotypes were detected.Among the four populations,the haplotype diversity was highest in the semi-desert of central Inner Mongolia(CIM)and Alxan desert(ALX),and lowest in Xinjiang-Gansu desert(XG).The nucleotide diversity was highest in North Xinjiang desert(NX),and lowest in the central Inner Mongolia(CIM).Analysis of molecular variance(AMOVA)revealed that genetic variation within the populations was 48.32%,however among the populations was 51.68%.F_ ST analysis showed that the differentiation was significant(P<0.05)between the populations in the semi-desert of central Inner Mongolia(CIM)and Alxan desert(ALX),and was extremely significant(P<0.01)among other populations.A phylogenetic tree of haplotypes disclosed three lineages of the great gerbil.Two main lineages comprised the individuals from China,in which the divergence time was more than 93 000 years ago.The third lineage,which was the basal one,just was composed of one individual from Iran.Nested clade analysis(NCA)indicated several population events were existed in different hierachical clades,including allopatric fragmentation,restricted gene flow and continuous population expansion.Population demography analysis indicated that great gerbil experienced strong expansion during the past 11 900 years,which indicated that climatic oscillations in the last ice age might have obvious effect on great gerbil populations.