Study Of Genetic Diversity In Spanish Mackele (Scomberomorus Niphonius) And Anchovy (Engraulis Japanicus)

The PCR technique was used to amplify the mtDNA D-Loop in 20 individuals of Spanish mackerel collected from the southern coast waters of the Shandong Peninsula. The PCR products were accumulated, purified and sequenced. As a result, 410 bp nucleotide sequences of partial D-Loop gene were obtained (the primers and some of the marginal sequences were excluded). By using Genedoc to compare the sequences of these 20 individuals, 54 variation sites were observed, of which 2 are of base deletion, 1 base insertion, 43 transition sites, 7 transversion sites and 2 transition-transversion sites. The pairwise genetic distances were computed by MEGA. The UPGMA and NJ phylogenetic tree were obtained through the cluster analysis over the pairwise genetic distance. As estimated by DNASP, the number of polymorphic sites (5) is 54; the nucleotide diversity (Pi) and the average number of nucleotide differences (AT) are 0.02708 and 11.047, respectively. It may be concluded that the variation in mtDNA D-Loop of Spanish mackerel is relatively rich. The 20 individuals can be divided into two branches according to clustering indicating that this population may derive from two different maternal ancestors. As a result, mtDNA D-loop can be one of the genetic markers available for scanning the genetic diversity of intra-population and inter-populations.By PCR amplifying and sequencing four fragments of 400bp, 550bp, 400bp and 650bp were obtained respectively from ITS-1, 16sRNA, Cytb and Col gene of Engraulis japonicus from Huanghai and Donghai sea areas of China. The sequence comparison results show that Col fragment can be used for genetic diversity analysis of intra-species and inter-species for its suitable length and variation sites. Col gene fragment of Engraulis japonicus of different geographical populations are amplified and sequenced. By using Genedoc to compare the sequences of the 45 samples, no base deletion and insertion were observed and 45 variation sites were found which include 43 transition sites and 2 transversion sites. The pairwise genetic distances were computed by MEGA. The UPGMA and NJ phylogenetic tree were obtained through the cluster analysis over the pairwise genetic distance. The number of polymorphic sites(5), the nucleotide diversity(/>/) and the average number of nucleotide difference(AT) of the total population and geographical populations were estimated by DNASP. It is found that the 45 samples of the three populations are random distributing without any clustering phenomena and the parameters of intra-population are very similar to that of the total population, which suggests that the genetic diversity of different geographic populations is poor and these populations which have no obvious genetic differentiation might derive from one population of single maternal ancestor. This research, which provides new molecular level data for species identifying and resources evaluation of different geographical Engraulis japonicus populations in Huanghai and Donghai sea areas, fills up the blank in the fields of population genetics and molecular biology of marine animals.