Eighty-one haplotypes were obtained from the complete Cytochrome b gene (Cyt b) of 99 Laxmann’s shrew Sorex caecutiens collected from three populations (Daxing’anling, Xiaoxing’anling and Changbaishan Mountains) in Northeast China. There was high overall genetic diversity (0.9940) and no significant variation in the genetic diversity of these three populations. Analysis of molecular variance showed that the differentiation among the three populations accounted for only 2.48% of total variation, that between sampling locations accounted for 0.34% of total variation, and that variation within sampling locations accounted for 97.19% of total variation. Genetic differentiation was not correlated with geographical distance separating populations. The phylogenetic tree was constructed based on the Cyt b of S. caecutiens and on data downloaded from GenBank. The phylogenetic tree branched into three lineages. S. caecutiens from Japan's Hokkaido formed a small lineage.  S. caecutiens from Jeju Island, Republic of Korea, formed another small lineage. S. caecutiens from Northeast China and other regions of Eurasia formed a large lineage. There was no further obvious differentiation of the genetic structure on the Eurasian mainland. Median-joining network analysis showed results similar to the phylogenetic trees, which suggested there was no obvious genetic differentiation in S. caecutiens from the Eurasian continent lineages excepting the lineages from Hokkaido in Japan and Jeju Island in Republic of Korea. The correlation was weak between genetic

differentiation and geographical distance. The analysis of population history showed that S. caecutiens in northeast China had experienced population expansion.

本研究对我国东北地区3个种群（大兴安岭、小兴安岭和长白山山脉）的中鼩鼱（99个样本）Cyt b基因全序列进行分析，共获得81个单倍型。整体单倍型多态性为0.9940，显示东北地区中鼩鼱整体遗传多样性较高，3个种群的遗传多样性无明显差异。分子变异方差分析显示3个种群之间的分化占总分化的2.48%，种群内采样地的分化占总分化的0.34%，采样地内部遗传分化占总分化的97.19%。遗传分化结果显示中鼩鼱遗传分化与地理距离存在非正相关关系。结合GenBank下载欧亚其他地区中鼩鼱Cyt b基因全序列构建系统发生树，分化为3个分支：日本北海道分布的中鼩鼱构成1个小分支；韩国济州岛的中鼩鼱构成1个小分支；我国东北地区和其他欧亚大陆的中鼩鼱构成1个大分支，在这个大支上未显现进一步的遗传分化结构。中介网络分析也暗示除日本北海道和韩国济州岛外，欧亚大陆分布的中鼩鼱没有明显的地理系统分化，表现出遗传分化与地理关联性较弱。种群历史分析显示东北地区中鼩鼱经历过种群扩张。