Study. Based On 28srdna And Coi Gene Sequences Acridoidea Some Types Of Molecular Systems

Acridoidea,the most widely distributed,is a big family of Orthoptera.Many species of Acridoidea may damage agricultural crops and forests.So these insects are very important in economy.The classification of Acridoidea has been a controversial issue for a long time and is a hotspot of phylogenetic research of Orthoptera.Comprehensive studies have been done based on morphology,cell biology,acoustical mechanism,molecular biology and other aspects on the species of Acridoidea.Currently,however,studies on molecular systematics of the classification of Acridoidea are still limited.In this paper,partial species of Acridoidea(35 species,15 genera,7 families) are studied from molecular systematics.The partial COI and 28SrDNA gene sequence of 35 species,and two outgroup species,Anabrus simplex and Erianthus versicolor(Tetrix japoniea and Tetrix tubercarina as outgroup in Bayesian Inference phylogenetic tree of 28SrDNA data sets),were sampled in this study.The base frequences,base substitutions and genetic distances of DNA sequences have been analyzed by using Clustal X1.81,MEGA4.1,PAUP4.0 and MrBayesV3.1 softwares.Phylogentic signal have been tested via base substitution saturation analysis,g1 and PTP tests.Results show that there are strong phylogenetic signal in the data tests.Based on the analyses of COⅡgene sequences, we reconstruct the phylogenetic relationships of these species from family level by using Neighbor-Joining(NJ),Maximum Parsimony(MP),Maximum Likelihood(ML) and Bayesian Inference(BI) methods.Summarizing these results,we can draw conclusions as follows:1.It is found that the average content of A+T in COⅠgene sequences(not including outgroup) is 65.5%,and G+C content(not including outgroups ) is 34.5%,which shows a strong A+T bias. However,28SrDNA(504 positions) is well conserved with 339 invariable sits,162 variable sites (not including outgroups),low A+T%(30%),and high G%(34.7%),which is obviously different from COⅠgene.2.The average transition and transversion ratio of COⅠgene sequence is 1.04.Transversion is nearly equal to transition.Sequence substitution saturation analysis indicates that the substitution is not saturated.Most transition occurs between T and C,and most transversion occurs between A and T.The average transition and transversion ratio of 28SrDNA gene sequence is 1.23.Transition is just a little higher than transversion and there is no saturation phenomenon in 28SrDNA gene sequence.3.The genetic distance of COⅠgene ranges from 0.000 to 0.194,distance among families ranges from 0.100 to 0.200;the genetic distance of 28SrDNA gene is 0.000-0.019,distance among families is 0.000-0.100.4.MR NJ,ML,and BI method are separately used to reconstruct the phylogenetic relationships based on the data sets of COⅠgene,28SrDNA gene and combined data sets.The result from comparing these trees indicates that topology of all the phylogenetic trees have little difference. Phylogenetic trees derived from BI are somewhat different that derived from MP,ML and NJ mehods,which are similar in topology.And basal of the phylogenetic trees constructed by BI mehod are divided into three clades,which constitute paraphyletic group.5.Based on the comprehensive tree topologies,we can conclude:(1) Insect species of Gomphoceridae,Arcypteridae and Acrididae(not including Acrida cinerea) are clustered together in all phylogenetic trees,suggesting that they have rather near phylogenetic relationships,which was consistent with the traditional classification result.In addition,Gomphocerippus rufus representing Gomphoceridae,and Chorthippus aethalinus,Chorthippus liaoningensis and Chorthippus brunneus huabeiensis of Arcypteridae are also clustered together in all phylogenetic trees.Besides,Mongolotettix japonicus and Chrysacris changbaishanensis standing for Acrididae, and the partial species of Arcypteridae are clustered together in most phylogenetic trees.(2) The taxonomic status of Acrididae is uncertain in all phylogenetic trees.According to all phylogenetic trees,Acrida cinerea belonging to Acrididae and Mongolotettix japonicus and Chrysacris changbaishanensis of this family are not clustered together.(3) Insects species of Pamphagidae and Pyrgomorphidae are clustered together and are regarded as a sister group in some phylogenetic trees.However,they are not clustered together and respectively form a monophyletic group in other phylogenetic trees.(4) All the species of Catantopidae and most species of Oedipodidae are separately clustered together and individually constitute a monophyletic group.This study is a relatively large-scale analysis of mitocbondrial sequences and nuclear sequences of 7 families of Acridoidea.By studying their molecular evolution and phylogenetic relationships,it provides molecular evidence for the further phylogenetic study of family level of Acridoidea and helps to refine the systematic researches.It is needed more extensive study on the phylogenetic relationships of Acridoidea and we also need to increase the species and quantities of the samples in order that the taxa is more representative.Meanwhile,sequence length is prolonged to contain more genetic information.