中缅树鼩头骨及下臼齿几何形态与环境的关系

共选取分布于云南、贵州和广西地区的190个中缅树鼩头骨和32颗臼齿(第二、第三下臼齿),运用几何形态测量法对其头骨侧面、腹面、背面及下颌侧面的形态特征进行主成分分析、薄片样条分析,同时运用统计软件SPSS15.0对头骨和臼齿进行多维尺度分析,以探讨头骨及臼齿形态与环境之间的关系.结果表明,头骨侧面在研究多种群头骨形态时更适宜,更有参考价值;经过薄片样条法分析显示形变多集中在鼻骨和臼齿,这可能与中缅树鼩生存的气候和地理环境相适应;经多维尺度分析显示云南、贵州和广西地区的中缅树鼩头骨具有明显的地区差异,同时,对臼齿的分析显示,臼齿形态具有地区差异,这种变化可能与中缅树鼩生活环境的经度和纬度有关.综上,云南、贵州和广西地区的中缅树鼩的头骨具有形态变异,并且差异仅仅发生在种群水平,这可能反映了其对特定生态环境的形态适应.

Morphometrics investigation of the skulls, mandibles and molar in Tupaia belangeri from Yunnan, Guizhou, Guangxi

Tree shrews, native in south-east Asia, are diurnal mammals that share morphological features with insectivores and primates. This led to the assumption that tree shrews derived from a basal stock of Mesozoic insectivore Eutheria close to the origin of primates. Nowdays tree shrews are positioned as a separate order Scandentia with the extant species integrated into the families Tupaiidae and Ptilocercidae. Tupaia belangeri belongs to Scandebtia, Tupaiidae. They are small mammals of Palaearctic realm and Primarily inhabit in Southern China, India, and Southeast Asia. T. belangeri had the widest of distribution and occupies the highest of latitude in their family; and they were always inhabited in terrestrial, arboreal, mountainous forest and shrub areas. The analysis of shape is a fundamental part of many biological researches. Along with the development of statitics, so it had the sophistication of the analysis of these types of data. In the 1980s, a fundamental change began in the nature of the data gathered and analyzed, which focused on the coordinates of landmarks and the geometric information about their relative positions. This new approach, called"geometric morphometrics", which had benefits that lead Rohlf and Marcus (1993) to proclaim a"revolution"in morphometrics. Morphological divergence among taxa was estimated quantitatively by analysing the outline of the mandible. This method treats the mandible shape globally and provides continuous data which can be used to compute of phenotypic distances. In the present study, the morphological characteristics of the skulls, mandibles and molars (lower second molar and lower third molar) of T. belangeri distributed in Yunna, Guizhou and Guangxi were measured by geometric morphometric techniques, principal components analysis, discriminate analysis, thin plate spline and multidimensional scaling analysis. Principal components analysis showed the morphological characteristics of the lateral cranium were more valuable to be considered as morphological index, this could be the result of sense organs including the nasal cavity, orbit and the ear vesicle of lateral cranium in T. belangeri. In addition, significant morphological differentiations were observed in both nose bone and molars by using thin plate spline analysis, which may reflect its adaptation to geographical differences in climate and environment, morphological changes of nasal cavity can alleviate the cold air from the outside to the lungs effectively, but also reflects the rate of water loss, and water loss was related to the environment temperature, so the different ambient temperature may result in changes of nasal cavity morphology in T. belangeri. In addition, the size of nasal cavity may also reflect humidity conditions of its habitat indirectly. Therefore, the dual role of the temperature and the humidity may lead to difference of nasal cavity in T. belangeri which were distributed in Yunna, Guizhou and Guangxi. With multidimensional scaling analysis, it was showed that the morphological characteristics of skulls and molars were significant differentiate from three areas. Using multidimensional scaling analysis of molars, differences in molar may reflect different feeding habits, which may be related to longitude or latitude of their habitations. It showed that the second lower molar of the score (0.443,0.433) and three lower molars of the score (0.448,0.412) had the larger contribution on the first dimension from the diagram of dimension weights, combined with the results by multidimensional scaling analysis, changes of molar may be influenced by the longitude, in other word, it may be influenced by the condition of water. In conclusion, the morphological characteristics of the skulls and mandibles of T. belangeri distributed in Yunna, Guizhou and Guangxi can be distinguished at population level, which may indicated the geographical adaptation to the environment.