福建近海2个鮐鱼群体遗传结构与遗传多样性分析

Population genetic structure and genetic diversity analysis among 2 populations of Scomber japonicus from Fujian offshore area

测定了福建近海鮐鱼(Scomber japonicus)2个群体共62尾个体的线粒体DNA(mtDNA)控制区序列,探讨了闽东、闽南群体的遗传结构和遗传多样性.获得长度为864 bp的控制区全序列,在所分析的62个样本中,共检测到35个变异位点,定义了36个单倍型,平均单倍型多样性(h)为0.960,核苷酸多样性(π)为0.009 85,核苷酸差异数(K)为8.508,提示鮐鱼是一个遗传多样性水平较高的稳定的大种群.构建的单倍型邻接关系树和单倍型网络图均没有表现出明显的地理分布特征.分子方差分析(AMOVA)表明,遗传变异全部存在于群体内个体间,2个群体间具有相似的遗传结构.群体间和群体内的Kimura双参数遗传距离均为0.01.Tajima's D中性检验及核苷酸不配对分析暗示鮐鱼是一个平衡的大种群,mtDNA控制区符合中性理论进化.结果显示,福建近海鮐鱼遗传多样性较高,闽东、闽南群体间不存在显著的遗传分化.扩散能力、种群大小、栖息地环境和台湾海峡环流促进了鮐鱼2个群体间频繁的基因交流,可能是闽东群体和闽南群体具有相似遗传结构的重要原因.

Despite the resolving power of DNA markers,pelagic and migratory marine fish species generally show little geographical population differentiation.In chub mackerel（Scomber japonicus） population differentiation has been detected only at a transatlantic scale.Of special interest are marine species with Eastern-Southern Fujian distribution because of the possible effect of past and present day restrictions to gene flow between Eastern Fujian populations and Southern Fujian populations.Thus,analysis of the whole mitochondrial DNA control region was used to extensively investigate the genetic structure of the two populations.In total,62 individuals were screened from coastal waters in Eastern Fujian（n=31）and Southern Fujian（n=31）and then sequenced.The results showed that a total of 35 variable sites were found in the aligned sequences of 864 bp,and 36 haplotypes were identified.Only 4 of 36 haplotypes were present in the two populations,but with low frequencies,and each sample was almost exclusively represented by a unique group of haplotypes.High levels of haplotype diversity（h=0.960）,nucleotide diversity（π=0.009 85） and the pairwise nucleotide differences（K=8.508） were detected,indicating long and stable demographic equilibrium conditions and a high level of genetic diversity of S.japonicus.Neighbor-joining（NJ） phylogenetic tree and haplotype network were constructed based on the haplotypes from the two populations,which suggested that there was not any genealogy appearing.The AMOVA analysis by ARLEQUIN Version 3.1 also showed no genetic differentiation throughout the examined range which was in conformity with Neighbor-joining phylogenetic tree and haplotype network.The pairwise Kimura 2-paramter genetic distances calculated by the MEGA Version 4.0 were also small between the two populations.The demographic history of S.japonicus was examined by applying Tajima＇s D tests and mismatch distribution analysis,which indicated the shallow population differentiation detected for the two populations was not a consequence of a recent colonization but probably reflected populations in long and stable demographic equilibrium.By applying mitochondrial DNA control region sequences in combination with genealogical and frequency-based statistical approaches,our data showed high genetic diversity and genetically homogeneous population structure between the two populations in Eastern Fujian and Southern Fujian.Factors of strong diffusion capacity,big population size,habitat and oceanographic current in Taiwan Strait are suggested to be important in determining mtDNA lineage distribution.The knowledge on genetic diversity and genetic structure will be crucial for theoretical establishment of fishery management of the stocks.