基于线粒体COI和Cytb基因序列的北太平洋柔鱼种群遗传结构研究

Population genetic structure of Ommastrephes bartramii in the North Pacific Ocean based on the COI and Cytb gene sequences analysis

为准确掌握柔鱼的种群遗传结构,拟通过线粒体DNA的COI和Cytb基因序列分析方法对柔鱼不同产卵季节群体的遗传多样性和遗传结构进行研究。经PCR扩增与测序分别获得600 bp COI与481 bp Cytb基因序列。基于COI基因序列分析得到的单倍型数、单倍型多样性指数、核苷酸多样性指数及平均核苷酸差异数分别为24、(0.729±0.033)、(0.005 70±0.003 25)和3.421。基于Cytb基因序列分析得到的单倍型数、单倍型多样性指数、核苷酸多样性指数及平均核苷酸差异数分别为28、(0.852±0.016)、(0.006 45±0.003 73)和3.101。分析认为,北太平洋柔鱼2个产卵季节群体均具有较高的单倍型多样性指数和较低的核苷酸多样性指数。单倍型邻接树、两两群体间的Fst值以及AMOVA分析结果均表明,北太平洋柔鱼2个产卵季节群体间的遗传差异不显著,不存在显著的群体遗传结构。初步认为,该海域因缺乏地理上的障碍,加之北太平洋海流的作用以及柔鱼个体较强的游泳能力,使得群体之间具有较强的基因流。

Ommastrephes bartramii is an important economic species in the North Pacific Ocean, and the sustainable exploitation of this squid has become an attractive problem in the world. Mastering the population genetic structure of O. bartramii will provide the theoretical basis for scientifically assessing and managing the resources of this squid. Therefore, in this study the method of Sequences analysis of mtDNA COI and Cytb gene was used to reveal the genetic diversity and discuss genetic structure of two spawning season cohorts of O. bartramii in the North Pacific Ocean. 600 bp of CO1 partial sequences and 481bp of Cytb partial sequences were obtained by using PCR amplification and sequencing. The result revealed that the number of haplotype, haplotype diversities, nucleotide diversities and average nucleotide differences in COI sequences were 24, （0.729＋0.033）, （0.005 704-0.003 25） and 3.421 while in Cytb sequences were 28, （0.852~0.016）, （0.006 45~0.003 73） and 3.101 respectively. Two spawning season cohorts of O. bartramii were all characterized by higher haplotype diversity and lower nucleotide diversity. A shallow topology of haplotype neighbor-joining （NJ） tree showed no phylogeographic structure between 2 spawning season cohorts. Analysis of molecular variance （AMOVA） and the fixation indices （Fst） between 2 groups and among 7 populations showed that no genetic differentiations were detected from our study, and the genetic variance mainly came from individuals within populations. It was supposed that extensive gene exchange between two spawning season cohorts was attributed to absence of geographic barrier, influence of sea currents and high swimming speed of O. bartramii individuals.