高原鼢鼠(Eospalax baileyi)头骨形态的地理分化

运用单因素方差分析、主成分分析、判别分析和聚类分析,对高原鼢鼠(Eospalax baileyi)4个地区(临潭、天祝、玛曲和碌曲)8个地理群体的头骨形态特征进行综合分析,比较13个特征变量的地理分异,挖掘形态特征的主要变量,并探讨其形态变异与环境的关系。结果发现,群体间13个特征变量均存在显著差异,主成分分析表明13个头骨特征变量可用3个主成分来表述,其累计贡献率达96.981%。颅全长、上齿列长及齿隙长是高原鼢鼠头骨发生分化的主要变量。天祝种群与碌曲种群,及玛曲种群与临潭种群都有重叠,其中碌曲的两个种群相似性最高,玛曲种群和临潭种群与其他种群几乎无重叠,显示完全分化,聚类分析结果与判别分析结果一致。头骨形态与地理因子的相关性分析发现头骨形态大小与海拔成显著的正相关关系。综合分析认为地理隔离、栖息地海拔因子影响下的生态条件等是高原鼢鼠头骨分化的主要因素。

Morphological analysis of the skull of plateau zokors (Eospalax baileyi) from different geographical populations

Morphological variation stems from a number of sources, including environmental factors. The skull is the most complex part of animal skeleton. Studies on skull morphological variations can help uncover the taxonomic status of a species, age and other ecological characteristics of the populations. Qinghai-Tibetan Plateau (QTP) is a region with high degree of environmental heterogeneity and harbors a rich diversity of indigenous fauna. Plateau zokor belong to the genus Eospalax and are endemic to QTP. Zokors have a long evolutionary history that has resulted in specialized characteristics such as reduced eye size and sight, strong adaptation to hypoxia, and foreleg structure, and strong claws for digging. These make this species an ideal model for testing the role of environmental factors in shaping morphological features. The skulls of plateau zokor from eight geographical populations were collected from the northeast of QTP in Lintan, Tianzhu, Maqu, and Luqu of the Gansu Province. The morphometric measurements were taken and the geographic division of 13 morphological characteristics was compared and analyzed by a one-way analysis of variance and discriminant function analysis. The environmental influences on morphological differentiationwere discussed. The results indicated that there were significant differences in four morphological characteristics and highly significant differences in two morphological characteristics between the Lintan and Luqu groups, but there was only one significant morphological characteristic between the Maqu and Lintan groups, Lintan and Tianzhu groups, and Maqu and Luqu groups. Principal components analyses showed that the 13 main traits were represented by three principal components, and contributed to 96.981% of variations cumulatively stepwise discriminant function analysis showed the diastema length and total length had the greatest contribution to skull shape variation. A significant positive correlation between zokor skull size and altitude was detected. These findings suggested that geographical isolation and ecological conditions under the influence of altitude was the main factor shaping zokor skull differentiation.