Molecular Phylogenetic Analysis Of Some Species Of Megaselia Of China

Megaselia belongs to Diptera, Phoridea, Phoridae, Metopininae. It is the largest genus of Phoridae.1500 species have been described all over the world. Because of the large number of species, numerous of traditional taxonomy questions are existed. In the past year, its morphology had been studied. Based on mtDNA 12S rRNA gene and COI gene, this study reconstructed its phylogeny and offered a number of molecular evidences to the classification of Megaselia. The conclusion are showed as follows:1.12S rRNA gene of 335bp Megaselia sequence shows strong A and T bias, and the average content of A+T is 79.8%. COI gene of 760bp Megaselia sequence also shows strong A and T bias, and the average content of A+T is 68.8%. These sequence code 20 kinds of amino acids. The content of Ser, Asn and Lys are very high.2. These analysis of p-distance which has not been adjusted based on 12S rRNA, COI and 12S rRNA+COI gene show that, the ranges of variation are 0.015-0.115,0.103-0.161, 0.085-0.142. Their homology are very high, and the ranges of homology are 0.885-0.985, 0.839-0.897,0.858-0.915.3. The relationship of p-distance and R (radio of transition to transversion based on 12S rRNA, COI and 12S rRNA+COI gene) is consistent with the typical distance-dependent character. The result shows that all data contain strong phylogenetic signals.4. The phylogentic trees based on 12S rRNA gene of Megaselia have a bad support, and the phylogenetic, trees based on COI and 12S rRNA+COI gene have a better result. The result of phylogentic tree is showing that there is no differences from the morphology. The Phora holosericea as the outgroup is well separated from the roots of trees, and the species of Megaselia are grouped together. Species which have a closer relationship, such as Megaselia angustirostris and Megaselia diversa; Megaselia longiseta and Megaselia rufipes; Megaselia atrita and Megaselia flava; Megaselia pleuralis and Megaselia intonsa, are grouped respectively. The result of this paper can provide a molecule evidence in the species which have not a definite group, such as Megaselia atrita, Megaselia rufipes and Megaselia angustirostris. But the evolution status of Megaselia spiracularis and Megaselia propinqua need an extensive study. 5. We conclude that as an efficient marker, COI gene is suitable to solve the phylogentic evolution relationship of Megaselia.