| As the gigantic genus of Phoridae, Megaselia Rondani is small size and sexualdimorphism, more than60%of which are unisexual species. There exist many disputes aboutdivision of taxa in genus and current classification system. For phoridologists, identificationand phylogenetic reconstruction become two important problemes to be resolved. It is verydifficult to resolve these two problems by only using traditional morphological methods.DNA-based identification systems represent a promising approach to resolve this taxonomicimpediment. Aiming at difficulty in traditional taxonomy, we use DNA barcode to identifyand match species of Megaselia and study phylogenetic relationship of it.In this study, we choose54species (Megaselia spiracularis treated as two taxa) of8groups in2subgenus of Megaselia and mitochondrial DNA COâ… gene as molecular markerand extract total DNA from245samples. Finally116items from experiment and16itemsfrom NCBI are analysed. The average content of A T G C of132sequences analyzed isrespectively29.2%,39.0%,15.6%and16.2%. The content of base A and T is significantlyhigher than base G and C which shows the strong bias of A and T in mitochondrial genes.In NJ tree,22species of Megaselia containing18species that have sexual dimorphismare grouped separately with good support. It shows that the application of short segments ofmitochondrial genes COâ… 552bp sequence can effectively identify species and match maleand female. M.spiracularis is grouped as two braches with good support, and theirintraspecific nucleotide divergences are large. The reason may be cryptic taxa or incorrectidentification. M. tecticaula and M. atrosericea are grouped as one branch with good support,their interspecies divergences are small. This may be their genetic relationship is near.Statistical analysis shows that there are228pairs intraspecific nucleotide divergencesand7032pairs of interspecific nucleotide divergence in Megaselia,and the ranges areseparately from0.00%to4.88%(expect8pairs in M.spiracularis) and3.36%to12.77%. Theresult shows that range of sequence difference in Megaselia is similar with other groups, but alittle higher.In phylogenetic MP tree, Megaselia, Diplonevra, Dohrniphora, Ctenopleuiphora andPhalacrotophora are not separated well, and the average sequence differences among generais15.03%, There has some overlap between it and average differences within Megaselia. Thisprovides the molecular support of the paraphyly and polyphyly of Megaselia.8groups ofMegaselia are mixed together also, there is not an obvious phenomenon who group togetheras subgenus or group.This shows morphological classification features of8groups are notstable and overlapped, not the real reflection of phylogenetic relationship. |
