Sequence and phylogenetic analysis of complete mitochondrial DNA genomes of two grasshopper species Gomphocerus rufus (Linnaeus, 1758) and Primnoa arctica (Zhang and Jin, 1985) (Orthoptera: Acridoidea)

Background and aims: In Xia's taxonomic revision, Gomphocerus rufus (Linnaeus, 1758), Chorthippus chinensis and Phlaeoba albonema belong to the families Gomphoceridae, Arcypteridae and Acrididae, respectively; whereas in Otte's taxonomic analysis of Orthoptera, all three species belong to the subfamily Gomphocerinae, family Acrididae. Materials and methods: We determined the mitochondrial genomes (mitogenomes) of G. rufus, compared these with 10 other caeliferan mitogenomes, and performed phylogenetic analyses in order to clarify the relationships of the three families in Xia's taxonomic revision and which study is more accurate in defining the relationships of the three families. Furthermore, the mitogenome of Primnoa arctica (Zhang and Jin, 1985) was determined. This is the first mitogenome of the subfamily Catantopinae, superfamily Acridoidea. Through the comparison of mitogenomes from six subfamilies of the superfamily Acridoidea and one species of Pyrgomorphoidea, we hope to summarize a general law on the composition of the caeliferan mitogenome. Results: The two molecules contain the same set of mitochondrial genes for 22 tRNAs, 2 rRNAs, 13 proteins, and a non-coding, AT-rich region. The base composition, gene order, and codon usage of the two genomes conform to those reported for other caeliferan species. Both genomes possess the rearrangement of tRNA(Lys) and tRNA(Asp). Compared with their ancestral mitogenome, this is a significant difference between the mitogenome of the suborders Caelifera and Ensifera or other Metazoa. A stem-loop structure that is similar to a previously presumed one (that probably involved in replication initiation) was found at the A+T-rich region of each mitogenome. In the phylogenetic analyses, the species from suborders Caelifera and Ensifera cluster, respectively, as monophyletic groups, and the two suborders cluster as sister groups. Conclusion: Within Caelifera, the subfamily Gomphocerinae appears to be a paraphyletic group in the analyses of the protein-coding gene (PCG) dataset and a monophyletic group in the analyses of rRNA dataset. The subfamily Oedipodinae is a monophyletic group; superfamily Acridoidea is a monophyletic group, and Pyrgomorphoidea is a sister to Acridoidea. Regarding Xia's revision, the families Gomphoceridae and Arcypteridae are closely related, and the family Acrididae is a paraphyletic group. Overall, the phylogenetic analyses in our study are in accordance with Otte's taxonomic analysis.