title: Comparative and phylogenetic analysis of the mitochondrial genomes in basal hymenopterans.
abstract: The Symphyta is traditionally accepted as a paraphyletic group located in a basal position of the order Hymenoptera. Herein, we conducted a comparative analysis of the mitochondrial genomes in the Symphyta by describing two newly sequenced ones, from Trichiosoma anthracinum, representing the first mitochondrial genome in family Cimbicidae, and Asiemphytus rufocephalus, from family Tenthredinidae. The sequenced lengths of these two mitochondrial genomes were 15,392 and 14,864 bp, respectively. Within the sequenced region, trnC and trnY were rearranged to the upstream of trnI-nad2 in T. anthracinum, while in A. rufocephalus all sequenced genes were arranged in the putative insect ancestral gene arrangement. Rearrangement of the tRNA genes is common in the Symphyta. The rearranged genes are mainly from trnL1 and two tRNA clusters of trnI-trnQ-trnM and trnW-trnC-trnY. The mitochondrial genomes of Symphyta show a biased usage of A and T rather than G and C. Protein-coding genes in Symphyta species show a lower evolutionary rate than those of Apocrita. The Ka/Ks ratios were all less than 1, indicating purifying selection of Symphyta species. Phylogenetic analyses supported the paraphyly and basal position of Symphyta in Hymenoptera. The well-supported phylogenetic relationship in the study is Tenthredinoidea + (Cephoidea + (Orussoidea + Apocrita)).
authors.affiliation: State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Sheng-Nan
authors.initials: SN
authors.lastname: Song
authors.affiliation: State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Pu
authors.initials: P
authors.lastname: Tang
authors.affiliation: Institute of Plant and Environmental Protection, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097, China.
authors.forename: Shu-Jun
authors.initials: SJ
authors.lastname: Wei
authors.affiliation: State Key Laboratory of Rice Biology and Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Xue-Xin
authors.initials: XX
authors.lastname: Chen
mesh_terms: D000818:Animals; D001482:Base Composition; D003062:Codon; D019143:Evolution, Molecular; D023061:Gene Order; D050259:Genes, Mitochondrial; D054629:Genome, Mitochondrial; D006927:Hymenoptera / Q000145:classification* / Q000235:genetics*; D016366:Open Reading Frames; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D003062:Codon