Co ¢ò 18s Of Rdna Gene Sequences Of Some Types Of Molecular Systems Acridoidea Studies

Acridoidea, which has many species, is the biggest family of Orthoptera, distributes widely, and many of them can destroy crops and cause serious influence on human. Therefore these insects have very important economic significance. The classification of Acridoidea has been a controversial problem all the time and is a hotspot of phylogenetic study of Orthoptera.As to phylogenetic relationships of the classification of Acridoidea, It has been studyed at all levels for a long time such as morphology, cell biology and molecular biology. But there still exist many differences. So far, the people are still not reach consensus. Most scholars either study on mitochondrial gene, or nuclear genes, they seldom put the two genes together. In view of this situation, the paper is aimed at make clear differences in those points. The 682bp complete gene sequence of COII and 1803bp complete gene sequence of 18S rDNA of 23 species, and outgroup species, Tetrix japonica and Tetrix grossus of the Tetrigoidea and Stiphra robusta of the Eumastacoidea, were studied in this paper. First of all, the COII&18S rDNA gene sequences were amplified using PCR, and then sequenced directly through cycling sequencing method. The sequence alignment was done by ClustalX1.81. The sequence statistics were done via MEGA 4.1. Phylogentic signal analyses had been tested by g1, PTP tests and base substitution saturation analysis. Phylogenetic signal analyses under the Maximum Parsimony (MP), Neighbor Joining (NJ) and Maximum Likelihood (ML) optimal criteria were done by PAUP4.0. In MrBayes V3.1.2, Bayesian inference (BI) was used to reconstruct the phylogeny of 23 species(representing 3 families and 17 genera). According to such results, we can draw the following conclusions:1.Mitochondrial gene COII (682 positions) has 329 variable sites, accounting for 48.2%, and the average content of A+T is 70.5%(so the content of G+C is 29.5%), which displays a distinct A+T bias. Nuclear gene 18S rDNA (1803 positions) has only 43 variable sites, accounting for 2.4%, and the average content of A+T is 47.8%, which is distinctly different from COII gene.2.The average transition and transversion proportion of mitochondrial gene (COII) is 0.98, which means that the transition is same to the transversion. Most of the transition happens between C and T, and most of the transversion happens between T and A. The transition of nuclear gene (18S rDNA) is a little more than the transversion. Substitution saturation analysis of COII and 18S rDNA all data sets show that they are all no saturated trend.3.In the 23 species (representing 3 families and 17 genera), the genetic distance of COII gene is between 0.001 and 0.226, the genetic distance of 18S rDNA gene is between 0.000 and 0.194, the result shows that the sequences of COII gene and 18S rDNA gene are obviously conservative.4.The PTP test and tree length distribution analysis (g1) of COII and 18S rDNA all data set show that they have strong phylogenetic signal.5. Based on all data sets of COII,18S rDNA and combined gene(COII & 18S rDNA), three phylogenetic trees are reconstructed, such as MP, NJ, ML and BI method. By comprehensive analysis, we can draw the following conclusions:(1) From the phylogenetic trees, we can see that the insects of Pyrgomorphidae and Pamphagidae either separate or form sister groups. There exist differences compared with traditional methods. Therefore, the phylogenetic relationships of Pyrgomorphidae and Pamphagidae need to be discussed; (2) From the phylogenetic trees, we can see that the insects of Catantopidae form a monophyletic group except Eucoptacra, that is to say, the most insects of Catantopidae form a monophyletic group; (3) To some extent, the topological structure of the phylogenetic trees can support each other. Except confidence, Ecoptacra binghami and Eucoptacra kwangtungensis, Xenocatantops humilis and Xenocatantops brachycerus, Traulia szetschuanensis-Traulia aurora and Traulia minuta, Primnnoa mandshurica,Primnnoa arctica and Primnnoa ningana, all can stable together.It is consistent with systematic classification results.It is proved that molecular systematica can also be used for classification.This study analyzes the phylogenetic relationships of insects of Acridoidea (3 families,17 genera) based on mitochondrial gene and nuclear gene. To a certain extent, it can provide evidence for the further research of family level o f Acridoidea and help to refine the systematic researches. As to this problem, It is needed more further study on the phylogenetic relationships of Acridoidea. For example, we need to increase the quantities of the samples and the species and so on in order that the taxa is more representative.