从COI基因序列探讨叶甲科部分昆虫的系统关系

对叶甲科21种昆虫的COI基因（长度为716bp）的序列组成和变异情况进行了分析．结果表明，21种叶甲碱基T、C、A、G的平均含量分别为39．5％、13．9％、32．1％和14．5％，A＋T含量明显高于G＋C含量，密码子第三位点A＋T平均含量高达90．4％；该序列片段中共有315个碱基发生变异，变异率达到44％；核苷酸替换主要发生在C←→T和A←→T之间，第三位点的替换频率显著高于前两个位点．以中华萝摩叶甲（Chrysocus chinensis）为外群，采用MEGA4．0软件构建系统发育树．结果显示，21种叶甲聚为2大分支，叶甲亚科的种类形成一大分支，位于系统树的基部，较其他2个亚科分化得早；跳甲亚科与萤叶甲亚科共同聚为另一分支，二者的关系较之与叶甲亚科的关系更近．系统树所反映的三亚科间的关系与传统分类结果一致．

Discussion on the Phylogeny of Partial Chrysomelidae Insects Based on COI Gene Sequences

The 716 bp sequences fragments of COI gene of 21 species of Chrysomelidae were analysed. The nueleotide composition showed that the average contents of T, C, A and G were 39.5%, 13.9%, 32.1% and 14.5%, respectively. The contents of A＋T is obviously higher than that of C＋G,and come up to 90.4% at the third codon position. 315 variable sites existed in the sequences and the divergence of sequences was 44%; nucleotides replacement mostly occurs between C←→T or A←→T , especially at the third position. By regarding Chrysocus chinensis as outgroup, the phylogenetic tree is reconstructed based on molecular information by the softwares MEGA 4.0. Phylogenetic analyses reveal that these 21 species were assembled into 2 clades, one is the species of Chrysomelinae which located on the basis of the tree and diverged earlier than the others; another is the species of Galerucinae and Alticinae, which showed closer relationship with each other than with Chrysomelinae. It is found that the phylogeny among these 3 subfamilies have no difference from traditional classification.