Molecular Phylogenetics Of Exoristinae (Tachinidae: Diptera) Based On COI Gene Sequences

Exoristinae is a large group of the Tachinidae (Insecta, Diptera), and is wildely distributed in the world. Tachinid flies are found on all continents and most major islands, only absent from cold and high latitude polar regions and some small oceanic islands. Its members of life histories are exclusively endoparasitic on Lepidoptera during their larval stage. In this respect, they often play significant roles as natural enemies of herbivorous insects in ecological communities.Exoristinae in taxonomic classification are characterized by a combination of chaetotaxy, male terminalia and female reproductive habits. We used molecular technologies in this study: DNA extraction, COI gene amplification and sequencing,19 species of 10 genera,5 tribes of Exoristinae for a phylogenetic analysis, and Tachina breviceps, Peleteria Propingue of Tachininae, Chrysomya megacephala of Calliphoridae were regarded as out group, and by using Paup 4.0b and Mega 4 softwares, phylogenetic trees were reconstructed for showing the relationship of tribes of Exoristinae. The results show that:The base of COI sequences obvious bias in this 22 species, the average of base is:T=39.5%, C=14.8%, A=29.9%, G=15.8%, the highest A+T=69.4%. The high AT content is a common feature in base composition of insect gene sequences. The nucleotide substitution main occurred in the second and third site, transversion (Tv) is higher than transitionin (Ts) the second site, and Ts is higher than Tv in the third site. The average of Ts/Tv is 1.1, Ts slightly larger than Tv, not reached saturation.Ts+Tv between 0.000-0.170, Phorocera assimilis and P. liaoningensis is 0, Ts/Tv between 0.000～1.147, P. assimilis and P. liaoningensis is 0. The genetic distance between tribes is farer than genera and is farer than species. The P-distance as the horizontal axis, Ts and Tv respectively, the vertical axis plotted, according to the relationship between COI gene replacement of the saturation, Ts and Tv relations with linear growth, indicating that the two were not saturated.COI gene using the nucleotide sequence of some species of insects of the subfamily Exoristinae phylogenetic analysis. The topology of the phylogenetic trees generated were similar. Exoristinae is a monophyly, the relationship between tribes, genera and species is definite, and (((Eryciini+Goniini)+Blondeliini)+Exoristini)+Winthemiini constitute the clade. It is proved that COI gene is useful for inferring phylogenetic relationships in Exoristinae.