Study On The Phylogeny Of Some Species Of Pentatomidae Based On Mitochondrial Cytochrome B Gene Sequences

Pentatomidae is one of the biggest families in Hemiptera order,and many of them are all pests in agriculture and forest. Presently, most of study on the group are concentrated on morphology and the phylogenetic relationship among subfamilies and genus is not very clear. We selected mitochondrial DNA(mtDNA) cytochrome b (Cytb) gene as molecular marker, amplified 485bp sequences segment with a pair of universal primers for 4 subfamilies and 16 species of family Pentatomidae at first time, in order to clarify the phylogeny of them. All sequences were aligned using software ClustalX(1.8) , and molecular phylogenetic tree were reconstructed using software package MEGA2.1 and PHYLIP3.6a. Through sequences analysis, the result shows:1. Cytb gene 432bp sequences(not include the sequences of the primers) shows strong A/T bias, the average content of A+T is 69.9%, A/T bias is more conspicious at 3rd position, comes up to 84.9%. At the same time ,the content of nucleotide C at this position is very lower,the average is only 3.2%,and divergence among species is higher(0.7-6.9%.) .The sequences coded 144 ammonia acid, the ratio of variation comes up to 50.2%2. Among the nucleotide substitution of the sequences, transition is just a little higher than transversion (TS/TV=1.2). Most transition occurs between G and A, transversion has the bias of A→T too, most of them occurs in the 3rd position.3. Reconstructed the phylogenetic tree for 11 species of subfamily Pentatominae with methods of Neighbor-Joining (NJ), Minimum-Evolutio(ME), Maximum Likehood(ML) and Maximum Parsimony(MP), the tapnology of the trees are almost identical. These 11 species can be divided into 4 branches: the genus Plautia, Palomena and Eurydema formed a branch ,they are the evolutionary groups in the subfamily; Pentatoma and Menida formed a branch spectively, and the former has closer relationship with the branch 1; Erthesina located at the base of the tree ,formed a branch by oneself, and is much more original than others.4. The phylogenetic relationship among the 4 subfamilies are uncertain according to the reconstructed trees. Combined the sequences analysis with the traditional systematic classification, we support the opinion that Tessaratominae and Scutellerinae is a independent family respecyively. The phylogenetic relationship of them is : Tessaratomidae and Scutelleridae formed sister group and diverged earlier than Pentatonidae ; Pentatomidae is the most evolutionary group in Pentatomoidea as a monophyletic clade.5. The study indicates that Cytb gene is a useful molecular marker at the generic and species level for phylogenetic study, but still has some problem at subfamily level.