Morphology And Genetic Diversity Analysis Of Harpadon Nehereus

Harpadon nehereus is an important marine economic fish in China,which has been widely paid attention to in recent years.In this paper,we studied the genetic diversity of H.nehereus from three aspects:morphology,mitochondrial DNA and simplified genome.By comparing the genetic differences between different populations of H.nehereus,we provided a theoretical basis for further studies on the genetic diversity of H.nehereus.1.Study on population morphological differences of H.nehereusIn this study,morphological data of 234 H.nehereus from 9 coastal populations in China were measured by combining traditional measurement method with frame method.In this study,SPSS software was used to conduct multivariate statistical analysis on the data and compare the morphological differences among groups.The results showed that the cumulative contribution rate of the first six principal components was 66.253%,and the scatter plots of the first and second principal components showed that there was a great degree of overlap among the other groups except Zhoushan group.Cluster analysis showed that Haikou and Zhoushan populations were significantly different from other populations,while Zhangpu and Sanya,Ningde and Sanmen populations were similar in morphology.One-way ANOVA showed that there were 4-14 differences in morphological characteristics.The discrimination results showed that the first discrimination accuracy was 66.7%-100%,the discrimination accuracy of Qingdao and Zhangpu population was100%,and the comprehensive discrimination rate was 88.8%.In order to verify the accuracy of discrimination,the 12 most important parameters were selected to discriminate again,and the discrimination accuracy was between 53.3%and 100%.The discrimination accuracy of Qingdao population was 100%,and the comprehensive discrimination rate was82.7%.The two discriminant results showed that the discriminant analysis accuracy was high except for a few errors,and the morphological method could better distinguish different geographical populations.2.Population genetics based on mitochondrial ND2 geneMitochondrial ND2 gene was amplified by PCR and 1 046 bp gene sequence was obtained.19 variable sites were detected,and 18 singleton variable sites and 1 parsimony informative sites were detected,respectively.98 sequences were defined to 19 haplotypes,with a mean haplotype diversity（H_d）of 0.367 6±0.063 8 and a mean nucleotide diversity（P_i）of 0.000 4±0.000 4.The average genetic distance was 0.000 2-0.00 06,the genetic differentiation index F_ST0.05,and the genetic differentiation was not significant.The AMOVA results showed that the main genetic variation of the H.nehereus came from within the population（99.68%）.The phylogenetic tree showed that there was no population differentiation among the 19 haplotypes.The overall neutral test results were negative,significantly deviated from the neutral,indicating that the five geographical populations had experienced population expansion in history.Based on the variation rate of ND2 gene（2.5%-3.6%per million years）,it is estimated that there was differentiation and expansion in the population of H.nehereus in the late Pleistocene of Quaternary,which was about 18700-13 000 years ago.3.Population genetics based on simplified genomesBased on GBS technology,SNP of 5 populations of H.nehereus were analyzed to explore the genetic diversity and pattern of H.nehereus.The results showed that the average nucleotide diversity was 0.64-0.75.Compared with the average expected heterozygosity,the former is 0.476 2,while the latter is 0.360 9.The Heterozygotes was excessive and homozygotes was missing among populations.The results of the adjacency tree and principal component analysis showed that different populations were closely related to each other and had no obvious branch and pedigree structure.These results provide scientific data for revealing the genetic background and germplasm status of different populations of H.nehereus in China’s coastal waters,and also provide reference for scientific and rational conservation of H.nehereus resources.