Clam, Ruditapes Philippinarum Population Genetics And The Clam Division Molecular System Evolution

Vertical polyacrylamide gel electrophoresis (PAGE) was used to investigate the genetic variation among three populations of Scapharca subcrenata, which were collected from Haizhou Bay, Xiangshan Harbor, Liaodong Bay. Among 18 loci of 9 enzymes identified, the mean proportions of polymorphic loci (P_.95) of the three populations were 61.11%, 55.56%, 64.71%; the average heterozygosities ranged from 0.1689 to 0.177.The mean effective allele number of the three population were 1.4417, 1.3917, 1.4219. All the three populations of Scapharca subcrenata demonstrated high genetic variability. The heterozygote deficiency commonly existed in the populations of Scapharca subcrenata, the inbreeding coefficient of the three populations were 0.2140, 0.1232, 0.1797, respectively. Based on coefficient of genetic differentiation (Fst) and the number of migrants per generation (Nm), The genetic differentiation between Haizhou Bay and Xiangshan Harbor was low, Fst = 0.0448; among other geographic populations the differentiation were moderate, Fst = 0.0755, 0.0812. Clustering analysis also showed that Haizhou Bay and Xiangshan Harbor were clustered with priority, then Liaodong Bay joined the group. The genetic differentiation mechanism of geographic populations and the inbreeding coefficient were discussed.The biochemical genetics in four populations of Ruditapes philippinarum, which were collected from Pingtan Island, Haizhou Bay, Xiangshan Harbor, Liaodong Bay, were analyzed by polyacrylamide gradient gel vertical electrophoresis. The results showed that the percentages of polymorphic loci (P_.95) of the four populations varied from 62.5% to 75.0%, the average heterozygosities ranged from 0.2743 to 0.3387. The mean effective numbers of alleles in loci varied from -0.0667 to 0.0260, the populations of R. philippinarum demonstrated high genetic variability. Based on coefficient of genetic differentiation and the number of migrants per generations, the genetic divergence between the populations of Pingtan Island, Haizhou Bay and Xiangshan Harbor were infinitesimal, while the genetic divergence between the three populations and Liaodong Bay was slightly evident. Clustering analysis also showed that the populations of Pingtan Island and Xiangshan Bay were clustered with priority, then the population of Haizhou Bay joined, last the population of Liaodong Bay joined the group. The genetic differentiation mechanism of populations and the cause of indistinctively heterozygosity deficiency were discussed.Ribosomal RNA gene internal spaces ITS-2 fragment of Scapharca subcrenata coming from Haizhou Bay, Xiangshan Harbor, Liaodong Bay were amplified via Polymerase Chain Reaction. The PCR products were sequenced and the content of T, C, A, G is 26.1%,24.3%,27.3%,22.4% in ITS-2 fragment. The content of GC is lower than AT in ITS-2. 27 nucleotide positions were found variable, which included 3 deletions or insertions, 24 transitions and transvertions, 27 haplotypes were detected in all samples. NJ and MP molecular phylogenetic trees were constructed which showed that there in no obvious clustering phenomenon between different geographic populations. Phylogenetic analysis was performed to clarify taxonomic status of S.subcrenata, S.broughtonii, and T.granosa using ribosomal internal transcribed spacer regions ITS-1 and ITS-2.The PCR products were ligated into T-vector, cloned and sequenced. NJ and MP molecular phylogenetic trees were constructed which showed that S.subcrenata and S.broughtonii were clustered with priority, then T.granosa joined the group. The result also confirmed the correctness of dividing T.granosa into Tegillarca and S.subcrenata and S.broughtonii belong to Scapharca by Benson's bivalve classification from the theory of cell biology.