高原鼢鼠(Myospalax baileyi)不同地理种群的形态变异

Morphological variation of the plateau zokor(Myospalax baileyi)from different geographical populations

本文采用主成分分析和聚类分析两种方法,分析了高原鼢鼠(Myospalax baileyi)12个地理种群17项形态特征的变异。主成分分析结果显示,分析构建的雄性前3个主成分累积贡献率为78.483%,而雌性前4个主成分累积贡献率为79.587%。对种群间形态差异分析贡献最大的指标为颅全长、基长、后头宽等反映头骨大小性状,以及顶嵴、额嵴最小间距体现的颧弓扩张程度指标。主成分分析结果与聚类分析结果一致,12个地理种群分化构成两个大的地域性群体:一个由甘肃种群构成的甘肃群体;另一个由四川种群和青海种群构成的混合群体。两个地域性群体实际上反映出两个不同的分化方向:一个方向表现为头骨较小,顶嵴、额嵴相对分开即颧弓扩张程度小,如甘肃群体;另一个则表现为头骨较大,顶嵴、额嵴相对靠拢即颧弓扩张程度大,如混合群体。这种地域群体的形态变异可以解释为,地下洞道系统中环境因子选择作用对高原鼢鼠形态变化产生了重要影响。

The variation of seventeen morphological traits for plateau zokor （Myospalax baileyi） collected from twelve geo- graphical populations was analyzed based on principal component analysis and cluster analysis. The results of principal com- ponent analysis showed that the cumulative contributive proportions of the first three principal components for males and first four components for females were 78.483% and 79. 587% respectively. The skull characteristics included profile length, basal length, and occipital width and otherwise, coupled with the least distance between the parietal ridges and the least distance between the frontal ridges representing the extent of zygomatic expanding might become the most contributive factors for the morphological variation among populations. The results of principal component analysis and cluster analysis congruously revealed that the populations were divided into two large regional groups： the Gansu group and the mixed group including Qinghai and Sichuan populations. These results actually reflected two different directions of evolution ： one showed a lesser skull, divided parietal ridges and frontal ridges, such as Gansu group; another showed a larger skull, closed parietal ridges and frontal ridges, such as the mixed group. This morphological variation of regional groups may result from the selec- tion of environmental factors in the subterranean burrow system.