Morphological And Genetic Diversity Analyses Of Acanthopagrus Latus From Different Geographical Populations

In order to understand the germplasm and genetic diversity of coastal Acanthopagrus latus in southern China after experiencing overfishing,proliferative advection,and environmental changes,we focused on the genetic diversity of Acanthopagrus latus in eight coastal cities of southern China,and this study was mainly divided into two parts.The first part was morphological analysis of Acanthopagrus latus,and the second part was analysis of the genetic diversity of D-loop based on mitochondrial DNA(mt DNA).The research objectsin this study were collected from eight southern China cities where coastal Acanthopagrus latuslive mainly in,i.e.Fangchenggang,chinzhou,Beihai,Haikou,Sanya,Yangjiang,Shanwei and Xiamen.In previous studies on Acanthopagrus latus,there were no more than eight urban areas,so this experiment will provide more content and more precise results than previous studies.Morphological analysis,using cluster analysis,principal component analysis and discriminant analysis,showed that: KMO and Bartlett’s tests were performed in principal component analysis.The KMO value was 0.804,and the Bartlett’s sphericity valuewas 0,which justified the use of principal component analysis.By principal component analysis,seven principal components were identified with a cumulative contribution of 78.505%,among which principal component one contributed 33.084%,and the others contributed16.550%,9.696%,5.820%,5.04%,4.257%,and 4.058%,respectively.As shown by the loading factor matrix,the effect of principal component one was mainly dominated by the direction of fish body trunk level,followed by the direction indicator of fish body tail mainly in principal component two,and mainly dominated by body height in principal component three.As revealed by the scatter plot,various degrees of coincidence existed among the geographic groups.The highest degree of group coincidence was between Yangjiang and Xiamen.The Fangchenggang group and the Shanya groups,the Qinzhou group,and the Shanwei group had less coincidence.Using cluster analysis,it was found that the Sanya,Yangjiang,and Shantao groups clustered with the nearest Euclidean distances,then clustered with Haikou and Xiamen groups,while chinzhou,Beihai and Fangchenggang clustered separately.Such a distribution roughly corresponds to the geographic distribution,i.e.Leizhou Peninsula and the Qiongzhou Strait divides Acanthopagrus latus populations roughly into two parts.Finally,the discriminant analysis showed that the lowest discriminant rate was 71.2% from Beihai,and the remaining discriminant rates were all over 80%.Beihaidivergedprimarily from Yangjiang region,presumably because of geographic location and ocean currents.The genetic structure analysis by molecular D-loop sequences showed that the 320 full-length D-loop sequences of Acanthopagrus latusin eight coastal cities of southern China were 947-958 bp in length.A total of 29 deletion or insertion sites and 210 variant sites were detected,of which 142 were parsimony informative sites,68 were single variant sites,210 were overall variant sites,and268 were haplotypes.The haplotype diversity was 0.99843,and the nucleotide diversity was 0.01570,which was contrasted with the data from previous studies and were found to be a decreased state,indicated it was a decreased genetic diversity.In the cluster analysis,the eight populations were divided into East and West parts by Leizhou Peninsula and Qiongzhou Strait,and their genetic differentiation coefficients were-0.01268 ～ 0.46674,gene flows(Nm)were0.57126 ～ inf,and the genetic distance and genetic differentiation index between every two populations were both large,but the gene flow values were small.AMOVA analysis showed that the genetic variation was 33.62% between cohorts,0.32% within cohorts,and 66.26% among individuals within populations.Compared with previous data,there wasa decreasing percentage of variation between cohorts and an elevated percentage of genetic variation occurring between individuals within populations.In addition,the neutrality test showed that Tajima’s SD was-1.69477,Fu’s SFS was-23.68339,and nucleotide mismatches wasa single peak,indicating that Acanthopagrus latus in South China Coastmay have experienced population expansion.Overall,the genetic diversity of Acanthopagrus latusalong the coast of South Chinawas abundant,and differentiated by west and east of Leizhou Peninsula and Qiongzhou Strait,in where they can be divided into two parts,east or west,for management.