Genetic diversity analysis of different age of a Dalian population of the Manila clam Ruditapes philippinarum by EST-SSR

The genetic diversity and population structure of a Dalian (shihe) population of the wild Manila clam Ruditapes philippinarum with different ages were examined using SSR markers. The genetic diversity of the different ages ( 1 age, Agel; 2 age, Age2; and 3 age, Age3) was relatively high. Statistical analyses using POPGENE 1.31 and SPSS16. 0showed that the sites of Rp-11, Rp-12, ages (P< 0.01); the sites of Rp-20 remaining seven sites had no significant effective number of alleles was 2.3729, and expected heterozygosity were high heterozygosity was 0.514. The changes and Rp-19, was well as the number of alleles significantly differed among the three, Rp-24, Rp-27, and Rp-30 also significantly differed (P0.05). The average number of alleles per locus was 4.3095, the and the polymorphic loci percentage P(%) was 14. The observed heterozygosity; the average observed heterozygosity was 0.2335 and the average expected in the Ne and He age followed the trend Age2> Age3>Agel. The observed and expected heterozygosity for each age were 0.2357, 0.2546, and 0.2159, as well as 0.4951, 0.5286, and 0.5184, respectively. The Age2 genetic diversity index was higher than Agel and Age3, whereas genetic differentiation was relatively low among the three groups. Among them, the minimum Agel- and Age3-clam genetic distance was 0.0195, which was a small variation. In contrast, the genetic distance between Agel and Age2 was 0.0437, indicating a small range (0.0195-0.0437). From a numerical point of view, there was great genetic similarity among the three ages of clams, with an average genetic identity of 0.9655. Agel and Age3 have a genetic similarity of up to 0.9807, whereas the degree of similarity between Agel and Age2 was small (0.9572). The clams with different ages had a very high degree of similarity. The calculated average genetic distances using the UPGMA clustering method revealed a smaller genetic distance between Age3 and Agel clams than between Age3 and Age2 clams. Allele frequencies, calculated by the chi-square test, showed changes in the population structure with age, changes in parts of the gene, decreased allele frequency, and some alleles becoming fixed. The overall genetic differentiation was low, with an F, values of 0.0248 (P