Preliminary Study Of Characters And Phylogenies Of Cerambycidae Based On Mitochondrial Genes

Taxonomy of Cerambycidae was traditionaly based on outer morphology,despite great efforts, however, the taxonomic of Cerambycidae still remainsproblematic because of the limitation of morphological traits. Mitochondrial genescontain affluent genetic information, was frequently used in taxonomic identificationof insects, and the analysed results could be used in studying phylogeneticrelationship of insects. To date, mitochondrial sequences storage of Cerambycidae inGeneBand database remains limited, and molecular phylogenetic study based onhigher taxonomic level was rarely reported. Therefore, we chose mitochondrial COI,COII and16SrRNA genes as molecular markers for studying mitochondrial sequencecharacters and the phylogenetic relationship of Cerambycidae on various taxonomiclevels. The main results were showed as follows,(1)Complete or partial sequence of mitochondrial COI, COII and16SrRNA geneswere obtained from66longicorn beetles by using PCR amplification.31of the66longicorn beetles were from Lamiinae,24from Cerambycinae,5from Prioninae,2from Lepturinae, and1from Disteniidae. Average length of the three genes were1547.19bp,581.64bp and505.89bp, respectively. Conserved rates proportion were46.71%,34.36%and41.98%, respectively. The base composition was biased as theA+T content were66.61%,69.97%and72.66%, respectively. The third codonposition of COI and COII had the highest A+T content and the fastest evolve rate,while the second condon position were the most conserved. The most frequently usedcodon in COI gene was ATT(I), followed by TTA(L), GGA(G), and TTT(F), whileTGC was not exist. The most frequently used codon in COII gene was ATT(I),followed by TTA(L), TTT(F), and GAT(D), while Cystine was not exist. The initiationcodon of COI and COII prefer to use ATT(I), and the stop codon of COI mainly wasTAA, several adopted by TA, and no TAG was detected.(2)Occurred frequency of Transitions(Ts) and Transversions(Tv) were calculatedfrom MEGA5.05, Ts of COI, COII and16SrRNA genes occured less than those of Tv,and the R ratio(Ts/Tv) of COI, COII and16SrRNA genes were0.93,0.73and0.52,respectively. Ts most occored between T-C, and Tv was between T-A. Saturation existmore or less, especially for the third codon position of COI and COII genes. Ts and Tv of COI, COII,16SrRNA and Combained sequence showed linear relationship withuncorrected p-distance, suggest no significant saturation had reached and thesequence were useful in reconstructing molecular phylogeny.(3)Using MEGA5.05, uncorrected p-distance of intra-/inter subfamily were analysedbased on COI, COII,16SrRNA and Combained sequence, and the4distance tableshowed similar details. Based on combined sequence, Lepturinae and Aseminae havethe minimum distance with Chrysomelidae. Disteniidae recovered the higher andstable distance with subfamilies from Cerambycidae, suggest the rationality of thefamily placement of Disteniidae. Average p-distance between Plilus and the threePrioninae reached0.223, which was considered as subfamily level, suggest thesubfamily placement of Plilus. Within Cerambycidae, Lepturinae was sister toAseminae, Cerambycinae was close to Lepturinae and Aseminae, averageintra-subfamily distance of Lamiinae was less than that of Cerambycinae.(4)Molecular phylogeny of COI, COII,16SrRNA and Combained sequence werereconstructed by using maximum likelihood(ML) and bayesian inference(BI) methods.Phylogenies from single gene couldn’t performed as better as combined sequence, asthe higher confidence level and the more consistency with morphology. According tothe ML and BI tree from combined sequence, Asemiinae and Lepturinae divergedearliest, and Lamiinae and Cerambycinae recovered as monophyly whenChrysomelidae selected as outgroup. Disteniidae formed clade with Prioninae, but therelationship was robustly supported by high confidence level. Plilus was not formclade with Prioninae, suggest Plilus should placed out of Prioninae. WithinCerambycinae, Callichromini was sister to Xystrocerini, Cerambycini was sister toPyrestini, Clytini represent as monoplyly. Within Lamiinae, Acanthocinini,Desmiphorini and Xylorhizini located at the buttom of the phylogeny, Apomecyniniwas sister to Pteropliini, Agapanthiini was sister to Hippopsini, Lamiini was close toBatocerini and Dorcaschematini. Saperdini located at the top of phylogeny, andrepresent as monophyly.