Molecular Phylogeny Of The Tribe Delphacini(Hemiptera:delphacidae:Delphacinae)from China

The planthopper tribe Delphacini(Hemiptera:Delphacidae:Delphacinae)is the largest group in the family Delphacidae,which includes more than 1500 species distribute in every Zoogeographical Regions over the world;All species of them are plant feeders and some of them are plant pathogens vectors which always cause significant losses for agricultural crops.The taxonomy of this tribe developed rapidly since it was established.However,the generic taxonomy remain obscure to date,the status of some described genera,especially these monotypic genera are questionable.It is necessary to elaborate the classification of the tribe by using molecular methods.In the present thesis,the phylogenetic relationships among genera of the tribe Delphacini from China based on non-protein coding gene segments 28S rDNA and 16S rDNA,mitochondrial protein coding gene segments COXI and Cyt h partial genes were analyzed.The fragments of nuclear 28S rDNA and mitochondrial 16S rDNA,COXI and Cyt b partial genes of 70 representative species of 49 genera were amplified and sequenced.The aligned sequences are executed in MEGA to calculate the average content of A,T,C,G,conserved sites,variable sites,parsimony-informative sites and the ratio of transition and transversion(Ts/Tv);The pairwise distance obtains by using Kimura's 2-parameter model(K2-P).Maximum parsimony,maximum likelihood and Bayesian inference are chosen to reconstruct the phylogeny based on every single gene and combined genes.The results are as follows:1.The result of sequence variation analyses showed the sequences of 28S rDNA from the tribe Delphacini was 729 bp in length,including 194 variable sites,528 conservative sites and 113 parsimony-informative sites,and the percentage of A+T was 47.5%;16S rDNA was 482 bp in length,including 242 variable sites,236 conservative sites and 202 parsimony-informative sites,and the percentage of A+T was 76.5%;COXI was 537 bp in length,including 250 variable sites,287 conservative sites and 221 parsimony-informative sites,and the percentage of A+T was 68.8%;Cyt b was 588 bp in length,including 300 variable sites,288 conservative sites and 267 parsimony-informative sites,and the percentage of A+T was 73.1%;The average content of A+T is much higher than the content of C+G in mitochondrial genes.This strong A+T bias in nucleotide frequencies is similar to that of other insects.2.The analysis based on Kimura's 2-parameter model(K2-P)obtained the pairwise distances.The smallest genetic distance of 28S rDNA between outgroup and ingroup is 0.025,and the largest is 0.163;The smallest genetic distance between ingroups is 0.000,and the largest is 0.132;The smallest genetic distance of 16S rDNA between outgroup and ingroup is 0.151,and the largest is 0.260;The smallest genetic distance between ingroups is 0.000,and the largest is 0.239;The smallest genetic distance of COXI between outgroup and ingroup is 0.141,and the largest is 0.265;The smallest genetic distance between ingroups is 0.000,and the largest is 0.262;The smallest genetic distance of Cyt b between outgroup and ingroup is 0.234,and the largest is 0.365;The smallest genetic distance between ingroups is 0.000,and the largest is 0.354.3.The MP,ML and BI trees of representative species in the tribe Delphacini based respectively on 28S rDNA,16S rDNA,COXI,Cyt b,16S rDNA+COXI?28S rDNA+16S rDNA+COXI were reconstructed,and the resulting phylogeny indicated that:(1)The genus Javesella is a monophyletic group.(2)The genus Nilaparvata is a monophyletic group.(3)The genus Ecdelphax is a monophyletic group.(4)The genus Sogata is a monophyletic group.(5)The genus is a monophyletic group.(6)The genera Sogata and Miranus form a clade and they are a sister group.(7)The genera Metadelphax and Toya form a clade,show closer relationship.(8)The genera Eurybregma,Stiropis,and form a clade,show closer relationship.(9)The genera Monospinodelphax,Palego,Aoyuanus and Numata form a clade,show closer relationship.The tribe Delphacini is suggested to be devided into three subtribes.The genus Opiconsiva Distant is a junior synonym of Harmalia Fennah.