Molecular Identification And Phylogeny Of Stenochironmous Kieffer(Diptera,Chironmidae)from China

The family Chironomidae is one of the most common insect groups in aquatic ecosystems,which is a well-known environmental indicator as well,and plays an important role in the transportation of nutrients and energy in the aquatic food web.Stenochironomus is a special genus of the subfamily Chironomidae,whose larvae feed on submerged wood and dead leaves.Their heads become narrow and flat with adaptation to drilling wood.As male aults of Stenochironomus show great morphological similarity and bears a series of intraspecific,and diagmostic features of larvae seriously reduced as a result of convergent evolution,it becomes nearly impossible to identify this genus exactly merely based on morphology.To revise Chinese Stenochironomus,a primary barcode database was established based on our lab collections,aiming to lay the foundation for accurate identification of this genus in the future.Totally,15 species of Stenochironomous were identified,which of them,S.balteatus,S.okialbus and S.hastatus are 3 new records in China;female adults of S.inalemeus,S.koreanus and S.okialbus were firstly associated with males;and S.xianjuensis syn.n was formly proposed as an inferior synonym of S.okialbus;and 7 species new to science,S.daweiensis sp.n.,S latilobus sp.n.,S.parahastus sp.n.,S.pseudokialbus sp.n.,S.pseudosatorui sp.n.,S.separatus sp.n.and S.sinoborkenti sp.n.were described here.Besides,some intraspecific variations were put forward and a new key to males of Stenochironomus in China were provided.The Neighbor joining Tree(N-J)constructed with 51 standard barcodes generates 17 Operational Taxonomical Units(OTUs),representing 15 independent species reaffirmed by morphological work.Genetic distance analysis based on k2 p model shows that the interspecific genetic distance(> 13%)is far greater than intraspecific distance difference(<1%).The huge gap(Barcode Gap)between interspecific and intraspecific genetic distance indicates that DNA barcode technology is suitable for species delimitation of Stenochironomus.In order to explore the monophyletic and phylogenetic positions of Stenochironomus,phylogenetic tree was constructed using both Bayesian inference(Bayesian inference)and maximum likelihood method with concatenated sequences of 6 molecular markers(COI-3P,COI-5P,18 S,28S,CAD1 and CAD4).The two methods produced a consistent result that Stenochironomus Kieffer is a monophyletic genus,sister to Xestochironomus Sublette & With,while Harrisius Freeman is a sister group of the assemblage of the former two genera.