mtDNA COI基因在轮虫分子系统重建中的意义

为分析mtDNA COI基因在轮虫分子系统重建中的作用．扩增并测定了B．calyciflorus和B．quadridentatus mtDNA COI基因部分序列。通过对扩增序列和Genbank中其它轮虫序列进行比较分析．发现COI序列包含丰富的遗传信息。利用Kimura双参数法计算遗传距离，在属和物种水平上间存在不同程度的遗传分化。利用NJ和MP法构建基因树。各物种形成独立进化枝．在属、科水平上与传统分类结果基本一致．这说明COI在轮虫系统重建中具有重要意义。在种内不同的单元型之间存在着遗传差异，部分种类不同地理种群之间存在较大的遗传变异．因此在系统重建过程中要注意种内多态的影响。

A MOLECUALR PHYLOGENY OF THE RORIFERA INFERRED FROM mtDNA COI GENE

In order to evaluate the role mtDNA COI gene played in phylogeny study of rotifera, we amplified partial sequences of COI gene from B. calyciflorus and B. quadridentatus by Polymerase Chain Reaction (PCR). Other COI sequences of rotifers were acquired from Genbank. 291 variable sites, including 278 parsimonious sites, were found. The genetic distances calculated by Kimura 2-parameter algorithm indicated there were different degrees of genetic divergences at species and genera levels. The phylogenetic trees, which were constructed by NJ and MP method, were consistent with the tree based on morphological characters. Therefore, COI was a rather useful molecular marker in phylogeny reconstruction for rotifers.There were genetic divergences among subspecies haplotypes, especially among different geographical populations. The genetic distances between two haplotypes of B. calyciflorus (B. c-1 and B.c-2) and B. quadridentatus (B. q-1 and B.q-2) were 0.198 and 0.228, respectively.Accordingly, the effect of polymorphism of subspecies haplotypes should be considered during the construction of phylogenetic trees by molecular markers