The Study Of The Molecular Population Genetic And Phylogeny Of Mactra Veneriformis Using 28SrRNA Gene And ITS1

Mactra veneriformis belongs to phylum Mollusca, class Lamellibranchia, family Heterodata, genus Mactride. It is a kind of commercial bivalves, which is widely distributed into the coasts of China ( specially in Liaoning and Shandong Province).There are few reports about the molecular population genetic and phylogeny of the bivalve based on 28S rRNA gene and ITS1 gene. In This research , 28S rRNA gene and ITS1(internal transcribed spacer 1) were used to study molecular population genetic, and phylogeny of Mactra veneriformis which is distributed into nine areas: Dandong(DD), Zhuanghe(ZH), Pikou(PK), Panjin(PJ), Jinzhou(JZ), Tianjin(TJ), Yantai(YT), Lianyungang(LY), Ningbo(NB). The aims of the present study are to clarify the population genetic structure, to estimate genetic differentiation and to provide more detailed information about the differentiation of nine different geographic populations of Mactra veneriformis. The partial LSU(long subunit) rDNA (28S rRNA gene) sequences and the ITS1 sequences of nine populations were amplified and sequenced. The nine populations were measured and analysed by nucleotide sequences of the 28S rRNA gene and ITS1 gene. The 28S rRNA molecular phylogenetic trees showed that the genetic diversity among the nine population was between 0.002 and 0.056. The highest value was 0.056 between NB and YT, and the lowest value was 0.002 between PK and ZH. The ITS1 molecular phylogenetic trees showed that the genetic diversity among the nine population was between 0.006 and 0.056. The highest value was 0.056 between NB and YT, and the lowest value is 0.006 between PK and PJ. These results revealed that the level of genetic flow was high, and the genetic diversity of these nine populations was low. It was gene flow that led to high genetic identity among the nine populations. The comparison made within the values revealed that gene flow and genetic identity remarkably related to the distance among these population. The dendrograms based on 28S r RNA and ITS1 data were similar but not the same. The results by 28S r RNA and ITS1 revealed that there was closely relationship among the five districts of Liaoning Province. The UPGMA, NJ and MP phylogenetic trees of Nei's genetic distance for nine populations show that the nine populations of Mactra veneriformis could be divided into 3 groups: the group of Liaoning(PJ, JZ, PK, ZH, DD) , the group of Yantai(YT,LY,TJ), and the group of Ningbo(NB). In the three groups , it can be seen that the group of Liaoning is more closely to the group of Yantai. The results indicate that isolation of geographic distance plays an important role in groups division. It is possible Ningbo group were farther from other groups, isolation of geographic distance brought about higher differentiation in population. The close relationship among the group of Liaoning populations , may be due to the human activities for aquaculture, which brings a large number of migration of larvae from different populations into the same geographical location.