DNA Barcoding Of Clupeiformes And Gerres(Perciformes:Gerreidae)in Coastal Waters Of Mainland China Based On The Mitochondrial Cytochrome Oxidase Subunit I Sequences

Clupeiformes generally lives in seawater, brackish water and fresh water in temperate and tropic zone, the group plays an important role in the world fisheries, and it is one of the most important economic fish group in China with high nutritional, medical and research values. Gerres(Perciformes : Gerreidae?) has rich nutrition and delicious meat quality, its main distribution in China is the coastal waters of the south China sea and the east China sea, and some species of Gerres is very rare now. With the increasing deterioration of the global marine environment and overfishing, the fishery landings of Clupeid and Gerreid fish has been declining, and some species are dangered or even extinct, therefore, urgent measures should be taken to enhance the protection and rational utility of Clupeiformes and Gerres resource. Accurate species identification is the premise and guarantee of the related analysis. Since there are so many species of Clupeid and Gerreid fish, some relatives are morphologically very similar, and morphological characters are highly influenced by the environment and development stages, traditional morphological identification often is difficult, if not fail to distinguish species correctly. DNA barcoding is a molecular marker technology of precise and efficient identification of species, widely used in species identification. In order to achieve unambiguous species recognition and define species status, 652 bp segments of mt DNA cytochrome oxidase subunit I from 407 specimens representing 48 species of 24 genus, 4 families, 2 suborder of Clupeiformes and 405 specimens representing 6 species of the genus Gerres(Perciformes:Gerreidae) were analyzed, of which sequences of 317 specimens representing 25 species of 11 genus, 3 families of Clupeiformes, and 399 specimens representing 6 species of the genus Gerres were determined in this paper. 90 specimens representing 32 species of 19 genus, 4 families of Clupeiformes, and 6 specimens representing 5 species of the genus Gerres were downloaded from Gen Bank. The phylogenetic relationship of closely related species are also discussed in this paper. The main results are as following:(1)The average intra-species distances of 48 Clupeid species was 0.6%, of which the genetic distances within 45 species were less than 2%, which meeted the criteria of intraspecific genetic distance of Hebert, and verified their species status. Of the 24 genus, 18 genus formed monophyletic groups, suggesting that the COI gene can distinguish most Clupeid genus. There are two species in the nominate C.mystus, and C.nasus and C.brachygnathus were the same species, which verified the previous studies; T.vitirostris and T.mystax was placed in the same clade, and further divided into two monophyletic groups with relative short genetic disatance, suggesting that T.mystax and T.vitrirostris should be treated as 2 subspecies or recently diverged species. S.zunasi is divided into 2 distant related clades, indicating that there might be a cryptic species in S.zunasi or sequences download from Gen Bank were wrong in identification; E.thoracata and I.elongata were in the same clade, S.longiceps and S.lemuru of Sardinella was also in the same clade, the reasons might be the impact of interspecific hybridization or recent radiation evolution if the possibility of morphological identification error could be ruled out.(2) Except G.filamentosus, the intra-species distances with the remaining 5 species of Gerres are less than 2%, and inter-species distances were 124 times greater than intra-species divergence, much higher than the standard of 10 times of Hebert, suggesting that the COI gene is an effective molecular marker to distinguish species of Gerres. G.filamentosus was divided into two clades with high average genetic distances(13.8%), 92 times greater than the average genetic distances within clades 0.15%(0.1%-0.2%), suggesting that G.filamentosus are two species. G.lucidus and G.limbatu was found in the same clade in the NJ tree, they might be synonym or wrong identification.(3) This study demonstated that the partial mt DNA COI sequences are good DNA barcoding to distinguish species of Clupeid and Gerres species. But, it has limitations for recent speciation, hybrid species and the reconstruction of phylogeny of distant species and higher level taxa.To better identify Clupeid and Gerres species, independent nuclear markers and multidisciplinary evidences should be combined in further studies.