Comparative and phylogenetic analysis of the mitochondrial genomes in basal hymenopterans.

Sheng-Nan Song,Shu-Jun Wei,Xue-Xin Chen,Pu Tang

doi:10.1038/srep20972

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)).

Highlights

Tenthredinoidea[19,20,21]
Complete or nearly complete mitochondrial genomes have only been reported for eight species in the Symphyta
The first was Trichiosoma anthracinum, which belongs to Cimbicidae, as the first representative of Cimbicidae, and the other was Asiemphytus rufocephalus, belonging to the Allantinae subfamily of the Tenthredinidae

Summary

Introduction

Tenthredinoidea[19,20,21]. Within the Tenthredinoidea, the monophyly of Tenthredinidae is unclear with regard to Cimbicidae and Diprionidae[16,21]. The sequenced region of the T. anthracinum mitochondrial genome was 15,392 bp long, with 13 protein-coding, two rRNA and 20 tRNA (except for trnQ and trnM) genes, and a partial A+ T-rich region.

Results

Conclusion