基于COⅠ基因序列的东、黄海区野生与养殖大黄鱼遗传多样性分析

Genetic diversity of wild and cultured populations of Larimichthys crocea in the East China Sea and Yellow Sea based on COⅠ sequence

为研究野生与养殖大黄鱼（Larimichthys crocea）群体的遗传多样性,对大黄鱼8个野生群体及6个养殖群体共336个样本的线粒体COⅠ基因部分序列进行了扩增和测序分析。实验最终获得序列片段长621 bp,总变异位点38个,简约信息位点23个,单变异位点15个,其中野生群体包含38个变异位点,占总变异的100%,养殖群体包含8个变异位点,占总变异的21.05%。在所有样本中共检测出单倍型34个,单倍型多样性为0.587,核苷酸多样性为0.00194,野生及养殖群体单倍型多样性指数分别为0.714-0.952、0.000-0.581。大黄鱼养殖与野生两个组群间的遗传分化指数为0.04982,占总变异的4.98%,差异极显著（P〈0.01）,组群间群体间的变异占1.46%（P〉0.05）,群体内的变异占93.56%（P〈0.01）。以上结果表明,大黄鱼的遗传变异主要来自于群体内,养殖群体的遗传多样性显著低于野生群体,两者的遗传多样性程度均处于较低水平,养殖群体间或野生群体间不存在显著的遗传分化,而养殖与野生两大组群间存在着显著的遗传分化。此外,通过对群体遗传结构及进化树的分析表明,东、黄海大黄鱼应属于同一地理种群,但两者间存在较低程度的遗传分化现象,黄海的大黄鱼群体遗传多样性高于东海群体。本研究可为大黄鱼种质资源的保护和恢复提供理论依据。

The large yellow croaker （Larimichthys crocea）, mainly distributedin coastal waters of China and East Asia, is one of the most important economic marine fish in China, and represents the largest yield for a single species in Chinese marine net-cage farming. Nevertheless, because of exhaustive fishing, habitat degradation and high-density aquaculture, the genetic diversity of the species is at a low level, and mariculture of the species is facing serious challenges from germplasm degeneration and susceptibility to infectious disease agents. Studies of the large yellow croaker have focused on the comparison of genetic differences among culture populations, and few of them have reported on comparative analysis among a wide range of wild and cultured stocks. To study the genetic diversity of wild and cultivated populations, we amplified and sequenced the mitochondrial cytochrome oxidase I （CO 1） gene of 336 samples from eight wild populations and six cultivated populations. The amplified fragment was 621 bp, containing a total of 38 mutation sites which included 23 parsimony-informative sites and 15 singleton mutation sites. The results showed that the wild populations contained 38 mutation sites, accounting for 100% of the total variations, while the cultivated populations contained 8 mutation sites accounting for 21.05%. We also detected 34 haplotypes in all 14 groups, and these were characterized by high haplotype diversity （0.587） and low nucleotide diversity （0.00194）. The haplotype diversity index of the wild and cultivated populations ranged from 0.714 to 0.952 and from 0.000 to 0.581, respectively. The coefficient of gene differentiation （Fst） between wild and cultured groups was 0.04982, accounting for 4.98% of the total variance. There was an extremely significant difference （P〈0.01）, the variation accounting for 1.46% among populations （P〉0.05）, and accounting for 93.56% within populations （P〈0.01）. Analysis of AMOVA and phylogenetic trees revealed that the genetic diversity of the large yellow croaker was in lower level, and that the genetic diversity in cultivated populations was significantly lower than that in wild populations. In addition, the variation within populations contributed its major genetic variation, and there was extremely high genetic differentiation between wild and cultivated grouPs but not significant within populations. The large yellow croaker from the East China Sea and Yellow Sea should belong to the same geographic population, but there is still a low level of genetic differentiation among the two groups, the genetic diversity of Yellow Sea groups being higher than that of the East China Sea. This study can provide a theoretical basis for resource conservation and germplasm recovery.