施氏屋顶鼠和海南屋顶鼠的线粒体12S rRNA基因序列的歧异及其系统进化关系

屋顶鼠的两个亚种--施氏屋顶鼠和海南屋顶鼠的外形和毛色相似,在一些标本的测量记录中,它们间的主要区别特征之一的尾长与体长比却是不肯定的.在广东,海南屋顶鼠仅分布于粤西区,而施氏屋顶鼠则分布于其余区域.在我们的这项研究中,采用了9个分别来自于施氏屋顶鼠(龙门种群和香港种群)及海南屋顶鼠的样品进行了线粒体12S rRNA 基因的测序,在所分析的 385个核苷酸位点长度的片段中,包含有26个变异位点和14个简约信息点,观察到3个插入/缺失位点.通过邻接法和最大简约法重建这些鼠类样品的系统进化关系.相比于施氏屋顶鼠的香港种群,海南屋顶鼠与施氏屋顶鼠的龙门种群有着更紧密的亲缘关系.基于12S rRNA 基因片段的序列数据,本项分析不赞同把海南屋顶鼠分类成为一个亚种的观点,认为海南屋顶鼠的形态变化是自然选择的结果,并由此导致当地适应和地理隔离.

Sequence Divergence of Mitochondrial 12S rRNA Gene and Phylogenetic Relationship Between Rattus rattus Sladeni and Rattus rattus Hainanicus

The appearance and hair color between these two subspecies Rattus rattus Sladeni and R.r. Hainanicus are similar to each other. Their most major distinctive characteristic is the length ratio of tail to body. However, this characteristic was unstable in some measuring records. In Guangdong, R.r. Hainanicus is restrictedly distributed in the west region, and R.r. Sladeni is widely distributed in the other regions of this province. In this study, we detected the sequences of mitochondrial 12S rRNA gene fragments of 9 samples from R.r. Hainanicus and R.r. Sladeni (Longmen and Hong Kong populations). These 385 nucleotide positions of 12S rRNA gene fragment include 26 variable sites and 14 parsimony-informative sites. 3 insertion/deletion sites are observed. The phylogenetic relationships among these samples were constructed by Neighbor-joining and Maximum parsimony methods. The analysis shows that R.r. Hainanicus is more closely relative to the Longmen population of R.r. Sladeni than to the Hong Kong population of R.r. Sladeni. The sequencing analysis of 12S rRNA gene fragments is not agreement on the classification of subspecies R. r. Hainanicus inferred from the morphology and geographical distribution. The morphological variation of R.r. Hainanicus should result from the natural selection, which causes local adaptation and geographic isolation.