Abstract: Population divergence is a crucial step in speciation,and studies on patterns of intraspecific variation based on
morphological traits can be helpful to uncover and further understand microevolutionary processes. In this research,we made a comprehensive comparison on skulls of Chinese white-bellied rat (Niviventer confucianus)populations among five mountains in middle and western China. The results indicated that skull variables among these populations are significantly different. In addition,discriminant function analyses further uncovered that Chinese white-bellied rat populations in the Qinling Mountains and Sichuan mountains have diverged completely in their skull morphology. Except for those between the Qionglai and Xiangling populations,skulls between the rest of the populations in Sichuan have diverged significantly,as well 69.1% of skulls were correctly classified to their source mountains,and variables including median palatal length and upper diastema length contributed most to their divergence,implying that the divergence in skulls morphology among the five populations perhaps primarily resulted from their food habits. Our results also illustrate that more caution should be taken to establish and discriminate intra-specific taxonomy units (such as subspecies)for small mammals which occupy a large geographical range.

Key words: Geographical divergence, Morphological trait, Population, Skull, White-bellied rat (Niviventer confucianus)

摘要： 种群分化是物种形成过程中的关键一步,通过形态特征进行种内变异的探讨对揭示微进化过程具有积极
意义。本文以社鼠头骨为材料,通过SPSS 统计分析软件对采集自我国中西部5 大山系的250 号标本头骨形态变
量进行了判别函数分析,结果表明秦岭与四川各山系之间社鼠头骨已发生完全分化,而在四川各山系之间,除
邛崃和相岭山系外,其余各山系社鼠头骨形态已分化明显。腭长、上颌齿隙长等变量是各山系社鼠头骨样本发
生分化的主要变量,暗示上述山系之间社鼠头骨形态的分化可能主要来自于局部种群在食物资源及觅食习性等
方面的差异。除此之外,本文研究结果尚揭示了在对具有广泛分布的小型兽类进行种下阶元(如亚种) 的划分
时,需充分考虑形态特征可能存在的地理差异。

关键词: 社鼠, 种群, 头骨, 形态特征, 地理分化