| The Chrysomelidae is a large family of Chrysomeloidea (Coleoptera) and a very important group insects, as most of them are pests feeding on leaves and stems of plants and do great harm to agriculture. With the development of the technique of experiment, the research on Chrysomelidae has proceeded extensively and deeply at the molecular level. Mitochondrial DNA (mtDNA) is a kind of maternal transmitted gene, which has become an efficient marker in the study of molecular phylogeny and the construction of phylogenetic trees, because of its conservation and convenience for experiments. COII gene is a protein-coding gene in mtDNA and well known. It has been used for phylogenetic analyses of a wide range of species and divergence levels for their universal occurrence, sequence and structure conservation and abundance. The PCR technique was used to get fragments of COII gene of 15 Chrysomelidae species in China (representing 3 subfamilies and 11 genera). Another 7 sequences and an outgroup, Crioceris duodecimpunctata's corresponding fragment were download from NCBI. All the sequenced fragments were aligned using Clustal X and 462 nucleotide sites were analyzed using Mega 3.1, The conclusions were as following:1. Fragments of 540bp COII gene of 18 Chrysomelidae insects showed typical patterns of many insects, such as high A+T content (73.3%). Transitions were found to favour the direction of T→C, while transversions directionally favoured A→T. The rates of substitution in three different codon sites are not the same, the fastest in the third site and the slowest in the second site. The total 540bp COII gene sequence of all insects is coding 180 amino acids. Average variation rate of amino acids is 40.5%. All insects contain 19 kinds of amino acids, not contain Cys. The content of Leu and Ile are highest comparison with other amino acids.2. The ratio of transition and transversion(R) is 0.8.Transition and transversion have a good linear relation with genetic distance, and show variable distance-dependent transition/transversion (TS/TV) which revealed strong phylogenetic signals in the set of data.3. With Crioceris duodecimpunctata as outgroup, NJ MP BI trees of 22 species of Chrysomlidae insects were reconstructed based on COII gene sequence. There was nosignificant difference observed in the topologic structures of all phylogenetic trees. Most members of genera successfully came together with high node support while all 22 species formed two main branches, one includes Chrysomelinae and the other includes Galerucinae and Alticinae. Alticinae shows more close relationship with Chrysomelinae than Galerucinae, which contrary traditional taxology. This result supports the taxonomic system established by Latreille.4. As all trees indicated, Linaeidea aenea and Chrysomela populi always came together with high node support, which showed the close relationship between these two genera. Similarly genera Mimastra and Cneorane are close in phylogeny as well. The genera Humba Chen abnormally stayed in the branch of Galerucinae whose phylogenetic position needs further study.5. In genus Chrysomela, 4 species showed unilateral relationship. Chrysomela populi was proved as the species with the fastest evolutional speed while Chrysomela salicivorax was most original.6. The reconstruction of phylogenetic relationships of 22 species of Chrysomelidae based on the proteinic sequences showed the different evolutional speed of two genera (Aulacophora, Chrysolina) compared with the results inferred from gene sequences.7. The research on phylogenetic tree proved that COII gene is an efficient marker in study of the phylogenetic evolution of interspecies and intra-genus , also intra-subfamilies. However some ambiguous relationships were found among the samples so united analysis with molecular data of other gene marker and taxonomy is necessary when reconstructing the phylogenetic relationship.
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