关键词：
鲭科;细胞色素b;转录间隔区1;分子系统树;鱼类进化
摘 要：
鲭科(Scombridae)由15属51种表层洄游性海洋鱼类组成,广泛分布于热带和亚热带海域,是重要的经济鱼类。目前关于鲭科鱼类系统发生学的研究主要基于形态学特征。为了从分子水平上阐明鲭科鱼类的分类与系统进化关系,本研究扩增了鲭科7种鱼类的线粒体细胞色素b(Cyt b)基因1个含311个碱基的序列区和转录间隔区1(ITS1)的1个含644～692个碱基的序列区。采用多个生物软件对序列碱基组成进行分析,计算了Kimura-2parameter遗传距离、转换/颠换比等遗传信息指数。Cyt b和ITS1序列4种碱基平均含量分别是:A为22.8%、G为16.4%、C为31.2%、T为29.5%和A为13.5%、G为31.3%、C为38.7%、T为16.5%。基于Cyt b计算的鲭科鱼类种间遗传距离为0.0065～0.3335,平均遗传距离为0.1689;基于ITS1计算的金枪鱼族鱼类种间遗传距离为0.0032～0.2668,平均遗传距离为0.2025。Cyt b和ITS1序列的转换/颠换比分别为1.8和0.9。以竹荚鱼(Trachurus trachurus)和花鲈(Lateolabrax japonicus)为外群,并结合GenBank上鲭科24种鱼类的同源序列,构建NJ、ML和ME系统树。研究结果确认了金枪鱼属处于系统进化树的顶端,代表着最新演化的种类,是鲭科中最繁盛的一属,也是目前系统发育的高峰。所有分子系统树都表明鲣属、鲔属和舵鲣属显示与金枪鱼属很近的亲缘关系,它们均归入金枪鱼族。然而,研究结果与形态学上将金枪鱼属分为2个亚属的分类结果存在分歧。同时,本研究关于狐鲣属、平鲣属、刺鲅属和双线鲅属进化地位上的结果也不同于形态学的结果。故鲭科鱼类客观、科学的分类地位还需通过形态学、生态学和分子生物学的深入研究加以确认。
译 名：
Molecular phylogenetic analysis in Scombridae based on Cyt b and ITS1 fragment sequences
作 者：
QIU Fan,SU Yongquan,FU Mengna,WANG Jun (College of Oceanography an Environmental Science,Xiamen University,Xiamen 361005,China)
关键词：
Scombridae;cytochrome b(Cyt b);internal transcribed spacer 1(ITS1);phylogenetic tree;fish evolution
摘 要：
The Scombridae is a family of 15 genera and 51 species of almost epipelagic marine fishes that form the basis of important commercial fisheries throughout tropical and temperate waters of the world.The currently accepted classification of the family Scombridae is largely based on classical morphological studies.In order to clarify the taxonomy and phylogenetic evolution relationship of Scombridae fishes from the view of molecular biology,fragments with 311 bp of the mitochondrial cytochrome b(Cyt b)gene and 644-692 bp of the internal transcribed spacer 1 (ITS1)were amplified from 7 species covering 5 genera in the family of Scombridae.The average contents of A,G, C and T were 22.8%,16.4%,31.2%and 29.5%respectively for Cyt b analysis and were 13.5%,31.3%,38.7%and 16.5%respectively for ITS1 analysis.Genetic information indexes,such as Kimura-2 parameter genetic distance and T s /T v ratios,were generated by using a variety of biology softwares.The genetic distance between species within Scombridae ranged from 0.006 5 to 0.333 5 and from 0.003 7 to 0.266 8 respectively,and the mean was 0.168 9 and 0.202 5 respectively based on Cyt b and ITS1 analysis.The T s /T v ratios were 1.8 and 0.9,respectively.With Trachurus trachurus and Lateolabrax japonicus as the designated outgroups,phylogenetic trees,which include 24 additional homologous sequences of other Scombridae fishes from GenBank,were constructed based on the neighbour-joining(NJ),maximum-parsimony(MP)and maximum-likelihood(ML)methods.The results affirmed that the genus Thunnus is a monophyletic group and is the most advanced genus of Scombridae,which is consistent with morphological hypothesis.Within Thunnus,our molecular results did not support the morphological phylogeny that stated there should be two subgenera comprising the tropical Neothunnus and the more cold-tolerant Thunnus. All phylogenetic trees exhibited very close relationships among Katsuwonus,Euthynnus,Auxis and Thunnus, suggesting that they belong to tribe Thunnini.Moreover,the phylogenetic relationships of genera Sarda,Orcynopsis, Acanthocybium and Grammatorcynus based on molecular data were not the same as those of these four genera based on morphological studies.Our results indicated that an objective,scientific taxonomic status for Scombridae species needs to be confirmed through the studies of morphology,ecology and molecular biology.
