Molecular Phylogenetic Research Of Partial Species Of Coreidae (Hemiptera: Heteroptera) Inferred From COI Gene

Coreidae are a big family of Heteroptera. There are 250 genera, 1800species known in the world, and about 63 genera, 200 species known in China. Coreidaewhich is a kind of phytophagous insects and important pests of agriculture and foresthave been studied widely in many fields such as taxonomy, molecular phylogeny,biogeography, etc. However, there are still lots of debates on the phylogeneticrelationships among tribes and genera levels. Phylogenetic relationships of Coreidaehave been studied by external morphological characters, molecular characters,Isoenzymes, etc.The mitochondrial cytochrome oxidase subunit I (COI) gene is one of the mostwidely used genetic marker for molecular systematics of animals, especially in insects.In this research, the COI gene sequences were amplified by PCR, and then sequenceddirectly through cycling sequencing method. 726 bp sequences of 16 species ofCoreidae were obtained. Based on the analyses of COI gene sequences, wereconstructed the phylogenetic relationships of these species by using Neighbor-Joining(NJ), Minimum Evolution (ME), Maximum Parsimony (MP), Maximum Likelihood(ML) and Bayesian Inference (BI) methods. The conclusions are showed as follows:1) The average contents of T, C, A andG to COI gene of 16 species in Coreidae are37.0%, 14.9%, 33.4% and 14.8%, respectively, A+T content is 70.4%, while G+Ccontent is 29.6%, which shows a strong A+T bias. These sequences code 242 aminoacids and contain 20 kinds of amino acids, respectively. The contents of Set and Ile arethe highest.2) To these 16 species of Coreidae, ratio of transition to transversion (R) of COIgene sequence is 1; Transitions are the same with transversions; most transitions occurbetween T and C, while most transversions occur between A and T. Substitution of thesecond position of codons are the lowest: transition are 5.4% of all transition, whiletransversion are 1.9%. And Substitutions of the third position of codons are the highest:transitions are 71.4%, while transversions are 80.4%.3) The phylogenetic relationships among 16 species of Coreidae and outgroups which include Physopelta quadriguttata (Hemiptera: Pyrrhocoroidea) and Triatomamaculate (Hemiptera: Reduviidae) had been reconstructed. The results show that: towspecies of the Mictini s. str is a monophyletic group; two genera of Cloresmini is amonophyletic group; Coreus has a high relative relationship with Cletus.4) The five tree-building methods provide some questions: Homoeocerini is amonophyletic group or not? And why is the Plinachtus clustered with theHomoeocerini? Acanthocoris and Cordysceles belong to a monophyletic group or not?And are they belong to Physomerini? The relative relationships between Cordyscelesand Hygia seem to be high.5) The research on phylogenetic tree shows that COI gene is an efficient symbol instudy of the phylogenetic evolution of interspecies and intragenus, so it is a usefulmarker.