线粒体D-loop序列变异与东方鲀属鱼类系统发育

东方鲀属的红鳍东方鲀（Takifugu rubripes）是后基因组时代的一种重要模式生物。本研究中，利用东方鲀属11种鱼类（18尾）的D-loop基因序列，对东方鲀属鱼类的系统发育关系进行研究。经序列比对排定后，分析中D-loop序列有841个位点，其中395个位点为可变位点，267个位点为系统发育信息位点。分别采用邻接法（NJ）、最大简约法（MP）、最大似然法（ML）和贝叶斯方法构建了分子系统树。研究结果表明：（1）东方鲀属鱼类为一单系类群；（2）由横纹东方鲀（T. oblongus）和铅点东方鲀（T. alboplumbeus）构成的姊妹群位于这个类群的基部。此外，本属鱼类物种分类现状还需要进一步的澄清。

Phylogenetic relationships of the genus Takifugu (Tetraodontiformes, Tetraodontidae) tested by mtDNA D-loop region sequence variations

The pufferfishes of the genus Takifugu are East Asian fish, mainly distribute along the coastal region in western part of the Sea of Japan and the East China. This genus is attached more and more importance to researchers, for Takifugu rubripes, which is one species in it, has been a new model fish in the post-genomic era. The details of the phylogenetic relationships within the genus remain unresolved. In the present paper, mitochondrial D-loop sequences of 11 species of the genus Takifugu were determined and analyzed to test the present phylogenetic hypotheses. The sequence saturation analysis was inferred from the shape of the trend line, which indicated that the sequence was unsaturated and could be used in the following phylogenetic analysis. After alignment, the sequence compositions and variations were analyzed by using MEGA 3 software. There were 841 sites, among which 395 sites were variable, and 267 were informative. There was significant difference in base compositional bias between the ingroup and the outgroup species. The uncorrected p-distance matrix obtained from the analysis of the alignment of all D-loop sequences showed that the relationships among the different species were closely. Neighbor-joining, Maximum Parsimony, Maximum Likelihood and Bayesian methods were employed for phylogenetics analysis, respectively. Due to the SH test about the phylogeny hypothesis, we chose the Bayesian tree as our best tree in this paper. The Bayesian tree has described a more clearly phylogeny and the analysis also has pointed out the basal species in the genus. The results indicate that the genus form a monophyletic groups, with the sister group consisted by T. oblongus and T. alboplumbeus is the basal group of the genus. Our results also show some confusion about the taxonomy in the genus, according to the data and combined analysis with the morphological characters, we suppose some species are in fact synonymous in this genus, which suggest that the taxonomy should be clarified based on both molecular and morphological data in the future.