Molecular Systematics Study On Subfamily Iassinae From China

Iassinae belongs to Hemiptera,Auchenorrhyncha,Cicadellidae,it is one of the larger subfamilies of Cicadellidae with the variety of species.Its morphological identifying features are not very obvious,and the classification system also changes frequently.In order to further clarify the subfamily of the species composition and phylogenetic relationship,the systematics study of Iassinae is based on the DNA sequences of iassine,and the result researched from the molecular level of the subfamily is more objective and accurate.In this study,we selected COI gene and 28 S r DNA D2 to D3 area for molecular markers and 36 Iassinae insects were sequenced.As a result,34 COI sequences and36 28 S r DNA sequences were obtained.The mitochondrial genome of 6 Iassinae,2Idiocerinae and 1 Macropsinae insects were also sequenced in this study.Each subfamily with one species had been sequenced comoletely,while the remaining specimens only had a partial sequence because of the uncompleted control region.All the research materials and data are deposited in the Institute of Entomology,Guizhou University,Guiyang,China(GUGC).Based on the existing results,the phylogenetic relationship of Iassinae had been studied in this paper,and the main conclusions are as follows:1.The K2 P P-distances based on COI sequences datasets showed that the P-distances of Iassinae were between 2.3%-13.8%.COI gene used as the DNA barcoding of Iassinae lineages were confirmed,and 28 S r DNA D2-D3 area with a slower evolution rate,which is applicable to genus and higher taxa phylogeny study.In the mitochondrial genome,protein coding genes evolve faster than RNA genes,and the mitogenomes has the faster evolutionary rate than nuclear genes.2.Mitogenomes of Iassinae insects are mainly composed of 37 genes and a control region.The mitogenome of Trocnadella arisana had been completed with a length of 15,131 bp,and a 80.7% AT content.The gene arrangements of Iassinae insects are identical to the ancestors of insect type arrangement.However,T.arisana has a rearrangement with the inversion of trn I and trn Q,and the ND3 was inverted inIdiocerinae sp.The control region of Iassinae insects contains repeat sequences and stem loops.Protein-coding genes tend to use at the AT rich codon like ATT,TTA,TTT and ATA.All PCGs start with an ATN codon except the ATP8 use the TTG,and the GTT used in ND5 were also found in some leafhoppers.The termination codons in Iassinae lineages were TAA,TAG or single T.The t RNA secondary structures of Iassinae insects are the typical type of clover shape,except the trn S1(AGN)with the dihydrouridine(DHU)arm formed a loop,and the Krisna rufimarginata with a big variable loop.Each lr RNA has six domains with a total of 43 stem loop structures,and the sr RNA is composed of three domains with a total of 24 stem loop structures.3.The analysis results based on the partial gene and the mitogenome datasets supported the monophyly of the tribe Krisnini.Based on gene fragments,analyses supported that Batracomorphus in all phylogenetic trees formed a paraphyletic group.And phylochronolgy analysis indicated that this group originated in Tertiary of Cenozoic.Monophyly of the subfamily Iassinae had been confirmed based on the analyses of mitochondrial genome datasets.The analysis results based on the PCGs datasets supported the monophyly of the family Cicadellidae and the treehoppers were derived from leafhoppers,and the divergence time was occurred in Cretaceous.Due to the lack of experimental samples and data,this study has shortcomings.But the existing results and conclusions could lay a certain foundation for the subsequent studies iassine systematics.