Molecular phylogenetic relationships of 13 Sciaenidae species in the China Sea based on RAG1 gene sequences

The family Sciaenidae,commonly known as drums or croakers,are distributed in the Atlantic,Indian and Pacific Oceans.This family comprises of fresh,brackish and marine species and about 270 species in 70 genera.The classification and evolutionary relationships of Sciaenidae have always been hindered by the overwhelming mumber of species,wild distribution and lack of morphological specializations traditionally used in ichthyological classification.The confusion and debates have brought much trouble to the study of the phylogenetic relationships among Sciaenidae.In this study,to evaluate the phylogenetic relationship of Sciaenidae in the China Sea,the RAG1 genes sequences of 13 species within 9 genera were amplified and sequenced.After alignment,about 1 498 bp length fragments which could be used for sequence analysis were obtained.The genetic information indexes were generated using MEGA3.1 software and phylogenetic trees were reconstructed by Treefinder software.Of the 1 498 bp aligned base pairs,230 sites were variable,accounting for 15.4% of the total base pairs.Molecular phylogenetic tree was constructed based on the maximaum-likelihood(ML),neighbor-joining(NJ)and maximum-parsimony(MP)methods,with Anabas testudineus as the designated outgroup.Conclusions were drawn as follows:(1) The tree indicated the 13 Sciaenidae species in China were grouped in two clusters.(2) Johninae and Sciaeninae were clustered together in the basal position,suggesting they are most primitive groups among the family Sciaenidae,which supported the previous conclusions based on morphology.(3) The phylogenetic trees showed that Nibea derived from Sciaenidae earlier than Pennahia.However,the morphologic view regarding these two genera as the same subfamily was not well supported yet and further analysis using multiple genes with different evolutional rates was recommended.(4) O.argenteus and C.aureus might be grouped in two different genera of one subfamily.(5) Larimichthyinae was the latest derived clade,which supported the previous conclusions based on morphology.Due to the lack of high bootstrap values support,the species-level within this clade was not highly consistent with that based on morphology.