A Preliminary Classification On Baetinae Of The Chinese Mainland

The mayfly subfamily Baetinae is the biggest one of the family Baetidae,which has the largest number of species in the order Ephemeroptera.This group of mayflies is very difficult to research because they usually have very high species diversity,small to tiny body size,uniform external morphology of adults,reduced genitalia and high variety of nymphal structures as well.Furthermore,in recent decades of years,the classification characteristics of them have been shifted from those of imagos to nymphs.So to get reliable taxonomic results,the associations between adults and nymphs are key steps.As a new biological research technique,DNA barcoding has been widely used in the insect classification.It is very convenient and efficient in associating different life stages.And related researchs have been done on mayflies.Using this method(COI gene as markers)plus indoor rearing adults from nymphs and character matching,we preliminarily classify the Baetinae of the Chinese mainland based on both imaginal and nymphal materials.The specimens checked in this study were collcected from more than 20 provinces and automonous regions of the country.As a result,totally 33 species in 10 genera are identified.Among them,2 genera(Xyrobaetis gen.nov.,Paralainites gen.nov.)and 12 species are new to science.They are Baetis strigosus sp.nov.,B.rufomaculatus sp.nov.,B.rubrolineatus sp.nov.,B.tephraonotus sp.nov.,B.pictus sp.nov.,B.gracilis sp.nov.,Baetiella quadrispinata sp.nov.,B.polyspinosa sp.nov.,Baetiella sp.nov.,Acentrella polymaculata sp.nov.,A.plana sp.nov.,Nigrobaetis sp.nov.,Paralainites minisculus sp.nov..One species,Xyrobaetis silvaticus(Kluge,1983)comb.nov.,is transferred from the genus Baetis,the other,Nigrobaetis purpurata(Gui et al.,1999)comb.nov.,is transferred from the genus Pseudocloeon.Besides,other 9 species are first recorded from the Chinese mainland.The K2P genetic distances between partial COI gene sequences of different species are calculated and phylogenetic trees are also reconstructed with using Neighbor-Joining,Maximum Likelihood,Maximum Parsimony and Bayesian Analysis methods.The data shows that in Baetinae,the mean intraspecific genetic distance is 0.000 to 0.010,the congeneric interspecific distance is between 0.023 to 0.176,and the intergeneric genetic distance is from 0.193 to 0.283.The trees show that except Baetis,the other genera are monophyletic taxa with high supporting index but the topological structures between them are not stable.