长江口及邻近海域鮸鱼的遗传多样性分析

Genetic diversity of Miichthys miiuy in Yangtze River estuary and adjacent sea analyzed by mitochondrial COⅠ sequences

为了解长江口及其邻近海域鮸鱼(Miichthys miiuy)的群体遗传多样性,采用线粒体COⅠ基因测序,对长江口(崇明)及邻近海域(舟山)2个鮸鱼群体的遗传变异进行了分析。结果表明,599 bp的COⅠ序列中包含22个变异位点,其中简约信息位点7个。60个个体中,共定义了20个单倍型,平均单倍型多样性指数(Hd)为0.676 8±0.069,核苷酸多样性指数(Pi)为0.002 29±0.000 37,表现为高单倍型多样性和低核苷酸多样性。分子方差分析(AMOVA)表明99.12%的遗传变异出现在种群内,仅有0.88%出现在种群间。群体间的遗传分化系数为FST=0.008 83(P>0.05),2个群体间无显著遗传分化。NJ系统树显示,2个地理来源的单倍型没有明显的地理群聚和谱系结构。中性检验和碱基岐点分布(Mismatch distribution)分析结果表明鮸鱼群体可能发生过种群扩张事件。研究结果可为鮸鱼渔业资源的合理开发和利用提供必要的参考。

To assess the genetic variation of Miichthys miiuy in Yangtze River estuary （ Chongming） and adjacent sea （ZhouShan） , the genetic diversity of the two geographical populations were examined based on mitochondrial COⅠ partial sequences. A total of 22 polymorphic sites （including 7 parsimony informative sites） and 20 distinct haplotypes were defined in 60 individuals. The mean haplotype diversity and nucleotide diversity were 0.676 8 and 0.002 29 respectively, which showed high haplotype diversity and low nucleotide diversity levels. The hierarchical analysis of molecular variance （AMOVA） indicated that 99.12 % of the genetic variation occurred within the populations, whereas 0.88% of the genetic variation occurred among populations. No significant genealogical branches or clusters were recognized based on the NJ tree. Intra-group variation between populations was also insignificant （FST = 0.008 83, P 〉 0.05） . These results suggested that the M. miiuy populations from Yangtze River estuary （Chongming） and adjacent sea （ZhouShan） have no significant population structure. Tests of neutral evolution and mismatch distribution suggested that M. miiuy may have experienced a population expansion. The present study provides basic information for the conservation and sustainable exploitation of this species.