| Sciaenops ocellatus,which belongs to Perciformes,Sciaenidae,Sciaenopsonea,also knowned as Sciaenops and Red drum,etc,is one of the most popular fishing species in the world.The fish is native to the coasts of Florida and the Gulf of Mexico,and introduced to China in 1991.Researches about S.ocellatus are mostly focused on fish culture in China,but the status about its genetic resources is unknown.Therefore,in this study,morphological markers,mitochondrial markers and microsatellite markers were used to analyze the genetic diversity of different cultured populations of S.ocellatus to understand the resource status of S.ocellatus in China and provide theoretical basis for promoting the sustainable development of S.ocellatus farming industry.The major results are followed:1.Morphological comparison of four different geographical populations of S.ocellatusA total of 142 individuals from four culture populations(Bei Hai,Zhou Shan,Zhu Hai,Qing Dao)were collected,and eight measurable morphological indices were measured.Three multivariate statistical methods were used to analyze morphological differences among populations of S.ocellatus according to the proportion of six measurable traits.Three unrelated principal components were obtained based on principal component analysis,and the cumulative contribution rate was 80.2%.The morphological differences of the four populations mainly existed in the size of tail and kiss.Four discriminant functions of S.ocellatus populations were established.The comprehensive discriminant rate was 85.2%.Among the clustering tree constructed,the morphological differences were the greatest between Zhou Shan population and other populations,but a little small between Zhu Hai population and Qing Dao population.2.Genetic diversity analysis of four populations of S.ocellatus based on D-loop and Cytb sequencesThe Fst values between Zhou Shan and Zhu Hai populations,Zhou Shan and Qing Dao populations were 0.0667 and 0.2270 respectively,which reached moderate differentiation and relatively high differentiation level,and the analysis based on D-loop sequence showed that Zhou Shan and Bei Hai populations were at a relatively high differentiation level.However,based on the cytb sequence,the Fst value between Zhou Shan population and Bei Hai population was 0.2665,which reached a high degree of genetic differentiation.AMOVA analysis based on D-loop and Cytb showed that population variations mainly came from intra-population variation with 90.63%and 91.58%,respectively,indicating that the variations of four populations occurred almost within populations.The genetic distance among four populations was 0.0012～0.0242,and 0.0009～0.0115 based on haplotypes of D-loop and Cytb,respectively.The results of NJ tree constructed by D-loop and Cytb were similar,which these populations were divided into two categories.Bei Hai and Qingdao populations were clustered into one group,and Zhou Shan and Zhu Hai populations were clustered into one group.Using Larimichthys polyactis as the outer group,the NJ molecular phylogenetic tree of D-loop and Cytb sequences were constructed and revealed that there was no obvious differentiation among four populations.3.Genetic diversity analysis of four populations of S.ocellatus based on microsatellite markers(1)Polymorphism of microsatellite lociA total of 8 highly polymorphic microsatellite loci were screened,the average allele number and the average effective allele number were 30.25 and 22.607,respectively.The average values of observed heterozygosity(H_o),expected heterozygosity(H_E)and Shannon diversity index(I)were 0.423,0.9671 and 3.197,respectively.The polymorphic information content(PIC)ranged from 0.932 to 0.972,indicating that these microsatellite loci were highly polymorphic loci(PIC>0.5).The Fixed coefficient Fst of microsatellite loci was between 0.014 and 0.041(0.025 of average value),and the gene flow(Nm)varied from 5.865 to 17.779.(2)Population genetic diversityThe number of alleles and effective alleles in four populations ranged from 24.25(Zhu Hai)to 28.5(Bei Hai),and 17.352(Zhu Hai)to 19.926(Bei Hai),with 25.755 and18.135 of the average number respectively.The observed heterozygosity Ho range in four populations ranged from 0.381 to 0.460,and showed the lowest in Zhou Shan population,and the highest in Heihai population.The expected heterozygosity(H_E)ranged from0.940 to 0.942 with the lowest in Zhu Hai population and the highest in Qing Dao population.The average Ho and H_Ewere 0.413 and 0.941,respectively.Shannon diversity index(I)ranged from 2.996(Zhu Hai)to 3.083(Bei Hai).These results indicated that genetic diversity of four populations was relatively abundant.3.Analysis of population genetic structure and differentiationThe unbiased genetic distance of Nei’s among four populations of S.ocellatus was0.1370～0.3910,and the genetic similarity was 0.6764～0.8720.The UPMGA clustering tree showed that the genetic distance between Zhou Shan and Zhuhai populations was the closest,and the farthest between Zhou Shan and Qing Dao populations.AMOVA analysis indicated that most of the genetic variation of four populations came from intra-population variation,accounting for 98.20%.The genetic differentiation index Rst value indicated that inter-individual variation was the main source of intra-population variation.In summary,most of the variation of S.ocellatus comes from intra-group variation,and inter-individual variation is the root cause of population variation.S.ocellatus has rich genetic diversity. |
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