白尾鼹(鼹科:哺乳纲)下颌骨几何形态测量分析及地理分化研究

Shape variation in mandibles of Parascaptor leucura (Mammalia,Talpidae) based on geometric morphometrics: implication for geographic diversification

白尾鼹属为东洋界单型属,主要分布于中国西南山地、印度阿萨姆地区、孟加拉国、缅甸北部和老挝等地。由于白尾鼹分布区范围内地形、气候和生境十分复杂,很可能导致物种的地理分化。为此我们查看了分布区之内18个地区的49号标本的下颌骨,并基于几何形态测量的方法进行分析比较。结果显示所有的标本按照地理分布可分为3组(滇东北、横断山南段以及印度)。3组标本间的形态差异主要表现在水平枝上,其中下臼齿齿列的长度、下颌骨水平枝下缘的弯曲度以及水平枝中部高度差异最为明显,而上升枝对3个地理居群的区分能力较弱。其中滇东北标本的下颌骨最为平直,下臼齿列长度最短;而横断山居群的下颌骨弯曲度最大,下臼齿列最长。根据以上结果,我们推测3个下颌骨形态有明显差异的地理居群可能代表了3个不同的地理亚种或是不同的种。但这仍需要结合上颌骨的形态差异和遗传结构分析加以证实。

Parascaptor is a monotypic genus distributed across Asia, including Southwestern China, Assam （India）, Ben- gal, and Northern Burma and Laos, all of which possess extremely complex and diverse topography, climate and habitat. To test whether morphological diversification has taken place in these different environments, we examined the mandibles of 49 P. leucura specimens from 18 localities throughout the distribution area. Geometric morphometric analyses were used to examine the shape variations. The specimens were clustered into three groups--Northeastern Yunnan （ group 1 ）, Southern Hengduan Mountain （group 2）, and Indian groups （group 3 ） --congruent with their geographic distribution. We found important distinctions Among these different groups in the horizontal ramus shape such as the length of the lower molar row, the curvature of the ventral margin and the relative depth of the horizontal ramus. Among the three groups, the specimens from Northeastern Yunnan have the shortest molar row and the thinnest and most flattened horizontal ramus. Our results ira-ply that the three geographic groups may represent three subspecies or even full species, strongly warranting a taxonomic re- vision using comprehensive methods.