基于16SrDNA序列的中国沿海短蛸种群遗传结构

Population genetic structure of Octopus ocellatus in coastal waters of China based on 16S rDNA sequence

采用线粒体基因测序技术,对中国沿海7个短蛸(Octopus ocellatus)群体的遗传结构和变异进行分析,以探讨种群扩散潜力对遗传结构的影响。共测定了100个短蛸样本的485 bp的16S rDNA序列,经UPGMA聚类分析表明,中国沿海的短蛸群体存在着明显的种群结构。7个群体明显地分化为两大类群:一个类群由北方沿海的大连、烟台、青岛、连云港群体组成,另一个类群由南方沿海的上海、舟山和广东群体组成;两类群间存在14个固定核苷酸碱基的替换。两类群间的遗传分化系数FST和基因流Nm分别达0.878和0.069,并达到显著分化水平(P<0.05)。AMOVA检验表明,两类群间的差异有87.76%存在于群体间,而仅有12.24%存在于群体内。两类群间的净遗传距离为0.019,表明可能为中度的种内群体间分化水平。依据分子钟理论推断,两类群的分化时间约为晚更新世冰期。两类群的分化可能与短蛸缺乏浮游幼体生活史和无长距离迁移习性有关,基因流与地理距离间的相关性符合脚踏石模型,进一步证实了这一点。同时短蛸群体的这种分化格局还可能与晚更新世以来中国沿海海平面的反复升降和长江口淡水的阻隔有关。

Genetic structure of populations is greatly influenced by the dispersal ability of marine organisms.It seems intuitive that limited dispersal capability should result in greater genetic differentiation.Octopus ocellatus is a typical cephalopod species which shows limited dispersal potential.In this study,the effect of dispersal capa-bility on population genetic structure was tested on seven populations of O.ocellatus in coastal waters of China,by applying mitochondrial gene sequencing technology.A 485 bp segment of the 16S rDNA gene was sequenced and analyzed in 100 specimens.Results showed that strong genetic structure existed in seven O.ocellatus popula-tions.Two distinct clades with 14 fixed nucleotide base variation in the 16S rDNA gene region were detected： one was composed of four populations from northern coastal waters,including Dalian,Yantai,Qingdao,Lianyungang populations,the other consisted of three populations from southern coastal waters including Shanghai,Zhoushan,Guangzhou populations.The FST and Nm between the two clade were high,which amounted to 0.878 and 0.069,respectively.AMOVA test,which showed 12.24% of the genetic variation lied within populations and 87.76% lies between populations,further suggested there was genetic differentiation between the two lineages.The net genetic distance between the two lineage was 0.019,suggesting a moderate and intraspecific level of differentiation.The two lineages may diverge in late Pleistocene,suggested by molecular clock analysis.The divergence might be resulted from low dispersal ability in O.ocellatus at both larva and adult stages.Pattern of isolation by distance was observed in this species,further verifying this point of view.The frequent osilation of sea level during the late Pleistocene and the fresh water outflow from Changjiang River might also play an important role in the formation of genetic structure in O.ocellatus populations along China coasts.These findings will have important implica-tions for better exploitation and protection of O.ocellatus resources in China in the near future.