Molecular Evolution And Phylogenetic Analysis Of Some Species Of Anisoptrea (Odonata) Based On Cyt B Gene Sequence

Dragonflies and damselflies are not only nature enemy insects, but also medical and edible resource insects. They are recognized as being good indicators of the condition of aquatic and terrestrial ecosystems. Moreover, Odonata are good experimental materials in resolving the systematic evolution problem of "Palaeoptera". Odonata are also ecologically important because they are major predators in terrestrial and aquatic ecosystems. Odonata have been studied from such fields as Morphology, Taxonomy, Ecology, Behavioral Biology, Cell and Molecule Biology, Biogeography and so on. In phylogenetic relationship of Odonata, studies have been carried out by using genes of 16S rRNA, Cyt b, COI, COII and 12S rRNA in mitochondrial DNA, but this field has not to study in China. While in suborder Anisoptera, Studies of cytochrome b (Cyt b) have not been dealt with in and abroad. Cytochrome b is one of molecular markers which used widly in animal molecular phylogenetic studies. We used one primer pairs of insect to amplify about 626 bp's sequence of Cyt b gene as a molecular marker to analyze phylogenetic relationship of 19 species in China which belong to suborder Anisoptera, Odonata. Cutting off primer sequences of 5' and 3', we got segments of 576 bp. DNA sequences were aligned by using software of CLUSTAL X. Aligned sequences were input into MEGA2.1, PHYLIP3.6a and MrBayesV3.0 for phylogenetic analysis by using methods of NJ, ME, ML, MP and BI. We get the molecular phylogenetic trees. In each tree-building method, measures or algorithms of several parameters of distance were used, but all the tree-buildings show exactly the same results. The results as follows:1. Cyt b gene sequences (576 bp, not include the sequences of primers) show a strong A/T bias. The average content of A+T is 69.6% (13 species of Libelluidae: A=31.0%, T=38.6%, C =17.4%, G=13.0%; 7 species of Anisoptera: A=31.3%, T=38.3%, C =17.6%, G=12.8%). The high content of A+T varies acrossing to ammonia acid in the 3rd position. As a typical protein-coding gene, different changes have been taken in different positions as follows: the second is least, the first is higher and the third is highest, regardless of the codon usages' affection by A/T bias. A/T bias is more distinct at 3rd position, while the content of nucleotide G at this position is very lower.