| The genetic diversity and phylogenesis among four wild populations of clam Lutraria siebaldii in coastal Guangxi and Guangdong provinces and two populations of Lutraria philippinarum in coastal Hainan and Vietnam were analyzed by morphological variation,amplified fragment length polymorphism(AFLP)technique and mtDNA 16S rRNA gene fragment sequence comparisons.The results of this study will lay a theoretic foundation for the identification,genetic breeding and fishery management measures.The main results of this research are as following:1.Three analysis methods(principal component analysis,cluster analysis and discrimination analysis)were used for investigating the morphological variations of four populations of L.siebaldii and two populations of L.philippinarum.In the principal component analysis,three principal component were obtained,the contributory ratio of the three principal components were 47.52%,21.39%and 19.69%respectively,and the cumulative contributory ratio was 88.60%.The results of cluster analysis showed that samples of L.siebaldii from Qinzhou,Zhanjiang,Beihai and Fangchenggang were rather similar in morphology,whereas samples of L.philippinarum from Hainan and Vietnam populations differed greatly from the four populations of L.siebaldii in morphology,they had reached the level of species.Discriminant functions of the six populations were set up and the discriminant accuracy rate of P1 and P2 were from 80.0%to 93.3%and from 83.3%to 89.7%,respectively,and the comprehensive discriminant accuracy rate was 86.7%.2.AFLP technique was used to estimate population genetics of four populations of L.siebaldii and two populations of L.philippinarum,five primer pair combinations amplified a total of 438 loci in 176 samples from the four populations of L.siebaldii and two populations of L.philippinarum,and the average proportion of polymorphic locis was 85.16%,and average of 87.6 locis per AFLP primer pair combinations.39 population-specific locis were found in 438 detected locis,which may be used to distinguish the two clams.Estimates of the Shannon’s index and Nei’s index provided similar results.Genetic distance among populations the four populations of L.siebaldii ranges from 0.0287 to 0.0567,and was 0.0214 from two populations of L.philippinarum.At first Qinzhou and Zhanjiang populations clustered,then they clustered with Beihai population,at last they clustered with Fangchenggang in L.siebaldii,whereas Hainan and Vietnam populations clustered,and finally they clustered together by UPGMA method according to their genetic distances.Combined with genetic distance and cluster analysis,the four populations of L.siebaldii belong to the population level.The results of Analysis of Molecular Variation(AMOVA)revealed that the diversity of four populations of L.siebaldii and two populations of L.philippinarum was divided into two parts,20.14%from inter-population and 79.86%from intra-population.Significant test showed that the genetic differentiation of four populations of L.siebaldii and two populations of L.philippinarum(Φst = 0.2014,P<0.001)within and among populations were significantly.So the results indicated that the genetic variation within populations was the important factor reflecting on genetic differentiation.3.Mitochondrial 16S rRNA gene fragments amplified by PCR and sequenced in 115 samples from the four different geographical populations of L.siebaldii.A length of 449 bp of the gene fragment and a total of 15 haplotypes were obtained.The average haplotype diversity(Hd)was 0.230,and the average number of nucleotide differences(K)was 0.915.15 haplotypes of the four populations of L.siebaldii and other kinds of molecular phylogenetic tree can be seen,all haplotypes of the four populations clustered with L.arcuata,and then clustered with L.philippinarum as one clade,whereas as outside source populations of Ruditapes philippenarum and R.variegate clustered one clade,then two clades clustered together. |
