Population Genetic Structure Of Sthenoteuthis Oualaniensis In South China Sea

Due to huge biomass and high endurance for fishing, Sthenoteuthis oualaniensis isregarded to be the most potential species for marine bioresources exploitation in SouthChina Sea.Till now，However, The studies on its basic biological characteristics are lacking.And population genetic structure of S. oualaniensis in South China Sea is still unclear.As we kown, population is the basic unit of the exploitation and management of fisheryresources. Without the information about population genetic structure of S. oualaniensis,it is very difficult for establishing this resource exploitation and management systems.Therefore, in the present study, we analyzed the population genetic structure of6different geographical populations of S. oualaniensis collecting from South China Seausing microsatellite makers.This study mainly includes two parts: developing microsatellite markers for S.oualaniensis and analyzing population genetic structure of S. oualaniensis in SouthChina Sea using12microsatellite markers.(1) Developing microsatellite markers for S. oualaniensisIn this study, we use “the magnetic beads enrichment method” to construct the S.oualaniensis microsatellite fragments Library. Then200positive clones containingmicrosatellite fragments were obtained through two rounds of screening. After thepositive clones were sequenced, we designed153pairs of PCR primers according toprimer designing requirement. Using a collection of the S. oualaniensis groups (N=48)detected and filtered pairs of primers. At last we got21good polymorphic microsatellitemarkers for S. oualaniensis. The number of alleles per locus varied from6to32. Theobserved and expected heterozygosities ranged from0.188to0.890and from0.537to0.968, respectively. No significant linkage disequilibrium was detected among these loci.Five loci deviated significantly from Hardy-Weinberg equilibrium after Bonferroni’scorrection (adjusted P value <0.0025), which might have been due to the small sample size or the existence of null alleles. Null alleles may be present at four loci (estimatednull allele frequency>5%).(2) Analyzing population genetic structure of S. oualaniensis in South China Seausing12microsatellite markers.Using12good polymorphic microsatellite markers, we analyzed populationgenetic diversity among6different geographical populations of S. oualaniensiscollecting from South China Sea. A total of181alleles were detected among6differentgeographical populations of S. oualaniensis. The average number of alleles in allsamples is15.08, ranging from5to22. The average of observed and expectedheterozygosities for all “population: maker” groups varied from0.354-0.875and0.401-0.946, respectively. The average of observed and expected heterozygosities persample ranged from0.652-0.698and0.769-0.846. In all69“population: maker” groups,3loci deviated significantly from Hardy-Weinberg equilibrium after Bonferroni’scorrection (adjusted P value <0.00417).For analyzing population genetic structure of S. oualaniensis in South China Sea,Analysis of molecular variance (AMOVA) indicated that99.61%of genetic variationswere within populations, and little of genetic variations (0.39%) were found betweenpopulations. Overall FSTvalues were0.0391which showed low but significant geneticdifferentiation. The result of MDS analysis and Mantle test showed that there was nosignificant correlation between geographic and genetic distances (r=0.0696, P=0.605).The individual allocation analysis demonstrated that, when there are two hypotheticalpopulations, for the population from the eastern Zhongsha islands,80.8%individualsbelong to hypothetical population1. However75.9%individuals from the southernNansha islands belong to hypothetical population2. The individuals of the rest fourpopulations were almost equally allocated to two hypothetical populations. When thereare three hypothetical populations, the individuals of6different geographicalpopulations were almost equally distributed to three hypothetical populations.In short, there are2different populations of S. oualaniensis in South China Seawhich from the eastern Zhongsha islands and the southern Nansha islands. The otherfour populations just are a mixed population.The result will serve as a useful tool for population genetics and sustainableutilization studies of S. oualaniensis.