东印度洋、南海海域鸢乌贼种群遗传结构研究

Genetic structure of Sthenoteuthis oualaniensis population in the east Indian Ocean and South China Sea

为了解东印度洋赤道、南海海域鸢乌贼(Sthenoteuthis oualaniensis)种群遗传结构,更好地对鸢乌贼渔业资源进行合理的管理,测定了东印度洋赤道北部和南部、南海北部和南部4个鸢乌贼群体共120尾个体线粒体DNA细胞色素b(cytochrome b)基因,分别对东印度洋赤道、南海海域鸢乌贼种群遗传结构展开研究。结果显示,4个群体总的核苷酸多样性与单倍型多样性为0.27332和0.981,其中南海北部海域群体的单倍型多样性最高为0.989,南海南部海域群体核苷酸多样性最高为0.30660。构建的单倍型网状图和系统发育树显示,东印度洋和南海群体间遗传分化显著。分子方差分析结果显示,遗传变异54.90%来自于组群间;群体间的F_(st)(F-statistics)分析表明,东印度洋赤道北部和南部群体F_(st)值为0.08588,南海北部和南部群体F_(st)值为0.02536,表明南海两个群体间不存在显著的遗传分化,东印度洋两个群体间遗传分化较小。东印度洋赤道两侧频繁的洋流活动可能是导致赤道南北群体遗传分化的重要因素,而东印度洋与南海之间的地理隔离则导致两个地理群体间遗传分化显著。综上所述,东印度洋赤道、南海海域鸢乌贼群体是两个独立的群体,在渔业管理上也应视为两个独立的管理单元。

Purpleback flying squid,Sthenoteuthis oualaniensis,widely distributed in tropical and subtropical waters such as the equator in the Indian and Pacific oceans.The species possesses fast growth rate,strong reproductive capacity and short life cycle,occuping an important position in the marine ecosystems.Sthenoteuthis oualaniensis is not only the predator of zooplankton,lanternfish and other organisms,but also the food source for many marine predators,therefore,the changes of its resources have a profound impact on the entire ecosystem.At the same time,it has a relatively high resource abundance.Sthenoteuthis oualaniensis possesses a large resource in the Northwest Indian Ocean and the South China Sea,with high potential commercial value.It is gradually becoming one of the important fishery species.As the basic unit of fishery management,researches on the population structure of Sthenoteuthis oualaniensis are crucial to the rational evaluation and management of fishery resources,and it is also important for the scientific management and rational maintenance of Sthenoteuthis oualaniensis fishery resources and genetic resources reference.Due to the complex current changes in the equatorial waters of the East Indian Ocean,researches on the genetic structure of Sthenoteuthis oualaniensis have not yet been reported.Whether there are genetic differences between groups still needs further researches.Population genetics are helpful in understanding the population structures and genetic variations in this sea area.The South China Sea is an important economic sea area in China,and there are important fishery resources available for exploitation,among which Sthenoteuthis oualaniensis resources are the most abundant species.It should be further developed and utilized.Further understanding of the genetic structure of Sthenoteuthis oualaniensis population in the South China Sea is extremely important for its’sustainable development and utilization in the South China Sea.Whether there are genetic differences between Sthenoteuthis oualaniensis of the East Indian Ocean equatorial waters and the South China Sea,and whether genetic differences are significant also require further study.Therefore,the mitochondrial cytochrome b gene(Cytb)marker was selected in this paper to analyze the genetic structures,genetic differences,genetic diversities,and population historical dynamics among four Sthenoteuthis oualaniensis populations in the East Indian Ocean and South China Sea.This would provide scientific basis for the management and utilization of Sthenoteuthis oualaniensis fishery resources,as well as the protection of genetic diversities.This research was conducted to understand the population genetic structure of Sthenoteuthis oualaniensis from the East Indian Ocean and the South China Sea,and to rationally manage the resources of squid fishery.The cytochrome b(Cytb)sequences of 120 mitochondrial DNA from four subpopulations of Sthenoteuthis oualaniensis were measured.These samples were collected from the north and south of the East Indian Ocean and the South China Sea.Cytb gene marker primers were used for the PCR amplification and sequencing,and a total of 120 Sthenoteuthis oualaniensis samples were genetically analyzed in four populations of the eastern Indian Ocean in the northern equator,southern and northern South China Sea.The results showed that the total diversities of haplotype and nucleotide were 0.27332 and 0.981,respectively.The highest haplotype diversity of the group from the north of the South China Sea was 0.989,while that of the group from the south of the South China Sea was only 0.30660.The results of the haplotype network diagram and phylogenetic tree showed that the genetic differentiation between populations of the East Indian Ocean and the South China Sea was significant.The analysis result of molecule variance indicated that 54.90%of population variation came from different groups,and the genetic differentiation was significant(P<0.01).The genetic variation rate within the population was 45.10%,and the genetic variation caused by geographical isolation was slightly higher than the variation of individuals within the population.The analysis of F_(st) value showed that F_(st) value between two groups from the north and south of the East Indian Ocean was 0.08588,and F_(st) value between two groups from the north and south of the South China Sea was 0.02536.These results indicated that the indistinctive genetic differentiation existed between two groups from north and south of the South China Sea,while the differences of the genetic differentiation between two groups from north and south of the East Indian Ocean were small.The frequent ocean activities of Sthenoteuthis oualaniensis in both sides of the East Indian Ocean were the main factor leading to the genetic differentiation in the north and south of the East Indian Ocean.While the geographical isolations between the East Indian Ocean and the South China Sea might be the main reason causing the prominent genetic differentiation between two geographical groups.The neutrality test results of the population in the northern Eastern Indian Ocean showed a very significant negative value(F s=-26.56809,P<0.01),and the nucleotide unpaired distribution map showed a significant undirected peak,which speculated that the population might experience a historical population expansion event.In conclusion,the two groups in the East Indian Ocean and the South China Sea were independent,therefore,they should be regarded as two independent units.Through the study of Cytb gene of 120 individuals in the north and south equatorial waters of the East Indian Ocean,the southern and northern waters of the South China Sea,this study revealed that there was a significant genetic differentiation between the East Indian Ocean equatorial sea area and the South China Sea area,which should be regarded as two independent groups in fishery management.The populations in both sides of the equator in the East Indian Ocean has moderate genetic differentiation,and the addition of Sthenoteuthis oualaniensis samples in the waters of the Strait of Malacca could preferably verify the speculation in this paper.The Cytb gene fragments used in this study could only reflect the genetic differentiation characteristics of the female parent,and there were certain differences in the evolution rate of different gene fragments and the phylogenetic information displayed.In the future,it is necessary to integrate other gene fragments or genomic DNA data more comprehensively.Moreover,in the future,morphological data information could be added,and combined with the population structure information reflected by the morphology,a more in-depth understanding of the population genetic structure of Sthenoteuthis oualaniensis could be obtained.