基于COⅠ基因序列的长腹剑水蚤系统进化关系

Molecular Phylogenetic of Oithona based on COⅠ sequence

长腹剑水蚤属(Oithona)是广泛分布于海洋近岸和外海海域的中小型桡足类中最为丰富的类群之一,由于个体小且形态差异微小,通过传统的形态学分类法对其进行准确鉴定难度较大。本文对南海分布的长腹剑水蚤属内的5个种,即瘦长腹剑水蚤(O.tenuis)、羽长腹剑水蚤(O.plumifera)、刺长腹剑水蚤(O.setigera)、伪长腹剑水蚤(O.fallax)和长刺长腹剑水蚤(O.longispina)线粒体COⅠ基因序列以及DNA数据库中长腹剑水蚤属其他地区种类COⅠ基因序列进行比较分析,使用ABGD(Automatic Barcode Gap Discovery)和GMYC(Generalized Mixed Yule Coalescent)模型进行物种界定,分析种间种内遗传距离,并构建系统进化关系。结果显示ABGD和GMYC模型均可以很好地对长腹剑水蚤进行种类划分;种内遗传距离为0.0%~1.6%,种间遗传距离为17.7%~44.5%(Kimura 2-parameter双参数模型),表明种间出现较高的分化;贝叶斯系统树和最大似然树进化树结果均表明,简长腹剑水蚤(O.simplex)与其他种类相距较远,羽长腹剑水蚤和拟长腹剑水蚤(O.similis)中存在隐种的分化,分别是我国南海海域和地中海的羽长腹剑水蚤以及朝鲜海峡和北海的拟长腹剑水蚤,种间遗传距离分别为18.6%、22.9%。

The genus Oithonais one of small size cyclopoid copepods which widely distributed and occurs in all kinds of marine environments（estuarine,coastal and oceanic waters）.However,routine identification of the species has remained challenging due to the small body size and subtle morphological differences among them.We started with a survey of species diversity in the genus Oithonain the South China Sea using a morphological approach,then obtained sequences from mitochondrial COⅠgene from several individuals of different species,performed tests on DNA taxonomy（ABGD and GMYC）and built a phylogenetic tree with the same gene sequence data download from DNA database.The results of delimitation using ABGD and GMYC model were consistent with morphological approach.The genetic distance within species was 0.0%-1.6% while 17.7%-44.5% between species.Both Bayes and Maximum Likelihood phylogenetic tree showed that each species was clustered together as a monophyletic group.O.simplexfirst separated from others species indicated pioneer speciation in Oithona.Two cryptic species were found in O.similis and O.plumifera,which were from the South China Sea and Mediterranean,Korea Strait and North Sea,respectively the genetic distance reached to 18.6% and 22.9%.