基于COI条形码的根口水母科Rhizostomatidae水母分子系统进化研究

为探讨DNA条形码基因COI序列在根口水母科Rhizostomatidae水母物种鉴定中的有效性,分析了根口水母科3属6种水母及口冠水母科1属1种共计265条线粒体COI基因同源序列,利用MEGA 3.0计算根口水母科种内与种间的遗传距离,并基于邻接法(Neibour-Joining,NJ)、最大似然法(Maximum Likelihood,ML)和贝叶斯法(Bayesian,BI)构建了其分子系统进化树。结果表明:4个属7种水母种类COI基因同源序列长度为482 bp,种间遗传距离为0.065~0.235,平均遗传距离为0.198,种内遗传距离为0~0.032,平均为0.006,其中种间平均遗传距离(0.198)显著大于种内平均遗传距离(0.006),种间遗传距离是种内遗传距离的33倍;根口水母科水母种间遗传距离均大于Hebert推荐区分物种的最小种间遗传距离(0.02);采用NJ法、ML法和BI法构建的分子系统树拓扑结构基本一致,同一物种不同个体间均能聚成独立的单系群,表明COI基因可作为根口水母科水母种类准确鉴定的有效条形码基因;系统进化树显示,海蜇属为单系群,系统进化分析结果与形态分类学的观点并不十分一致。研究表明,COI基因序列在根口水母科不同阶元间变异较大,适合于根口水母科水母种类鉴定及群体水平的分子标记。

Phylogenetic relationship of Rhizostomatidae based on COI barcoding marker

The 482 bp COI was sequenced in 265 individuals sampled from 7 species in 4 genera in Rhizostomatid-ae , the genetic distances in inter-and intra-species were calculated by MEGA 3 . 0 , and the molecular phylogenetic trees were constructed using Neighbor-Joining, Bayesian inference and Maximum Likelihood methods to investigate the feasibility of COI sequences as DNA barcodes to identify species in Rhizostomatidae. The results showed that the inter-species genetic distance was changed from 0 . 065 to 0 . 235 , with average of 0 . 198 , while the intra-spe-cies genetic distance was varied from 0 to 0 . 032 , with average of 0 . 006 , 32 times higher than that in intra-spe-cies. Moreover, each inter-species genetic distance value is higher than the minimum species identification value 0. 02 proposed by Hebert. The phylogenic analysis showed that the topology of the Neighbor-Joining tree, Maxi-mum Likelihood tree and the Bayesian tree was consistent each other and individuals of each species formed an in-dependent monophyletic group, indicating that COI was of an effective barcode gene for accurate identification of species among Rhizostomatidae. Meanwhile, the phylogenetic trees showed that Rhopilema jellyfishes are non-mon-ophyletic and different from morphological taxonomy. In conclusion, COI is highly divergent among different jelly-fishes in Rhizostomatidae and is an appropriate marker for species identification and population studies at the spe-cies level in Rhizostomatidae.