DNA Barcoding And Molecular Phylogeny Of Sciaenidae In Coastal Waters Of China

Sciaenid fishes play an important role in Chinese marine fisheries due to their significant economic value.For example,Larimichthys crocea and L.polyactis once occupied half of Chinese four main marine fisheries,and Megalonibea fusca,Bahaba taipingensis were very expensive.However,due to overfishing,marine environmental pollution and other anthropogenic influences,many Sciaenid fishes in China collapsed,and some fishes are on the verge of extinction.So far there were about 35 species,18 genera reported in coastal waters of China.Similar external morphological features in some species necessitated the supplement of internal anatomical characters as identification keys,thus the taxonomy of Sciaenidae is difficult,and phylogenetic relationships of some species are controversial.In present study,269 mtDNA COI sequences representing 34 species,18 genus of the Sciaenidae family collected in coastal waters of China were subjected to DNA barcoding analyses,and determined full lenght sequences of COI,Cytb and ND2 genes of 17 species in present study and homologous sequences of 24 species were combined to study phylogeny of China's Sciaenidae,with the aim to enrich Chinese Sciaenidae fish DNA barcoding database and investigate their phylogenetic relationships.The main results are as follows:In NJ tree all sequences were divided into 32 clades,which was congruent with ABGD analysis,and the average genetic distances among and within clades were 0.239(0.0376~0.399),0.0026(0~0.014)respectively,i.e.,the average interclade genetic distances was about 92-fold higher than the intraclade,forming obvious barcoding gaps.Except those clades comprising of only single sequences of one species,18 clades out of 28 clades(64%)consisted of sequences of one species,25% clades were mixing with multiple species,and 25% species were distributed to different clades,indicating that compared to DNA barcoding,there were great challenges in accurate identification of species by traditional morphological characters.Our findings supported the taxonomic treatment of Collichthys niveatus and C.lucidus as two different species.Protonibea diacanthus might have experienced recent evolutionary radiation or have a high genetic diversity.M.fusca and Pterotolithus maculatus might have introgressive hybridization,incomplete lineage sorting,or misidentication of morphological species.The phylogenetic relationship between Nibea coibor and N.soldado should be studied further.DNA barcoding failed to differentiate Argyrosomus japonicus and A.amoyensis efficiently,and frequent misidentication of morphological species occurred in Johnius.Although there were some difference in phylogenetic performances of 3 mtDNA genes,the main results were similar.Overall Larimichthys,Nibea and Collichthys were monophyletic.The taxonomic status of P.diacanthus were supported.Pennahia including P.argentatus,P.macrocephalus,and P.pawak,were monophyletic.Johnius was distantly related to the remaining taxa.Except Johniinae,no subfamilies were found to be obvious monophyletic,thus phylogentic relationships deduced from morphological characters should be re-examined.