New insights into the phylogeny of Tetrigoidea (Insecta, Orthoptera), with the announcement of the first mitogenome of the genus Phaesticus.

The mitochondrial genome (mitogenome) has been widely used to infer the phylogeny, origin and evolution of insects. Although mitogenomic data have been used to study the phylogenetic relationships of Tetrigoidea (Orthoptera), larger sample sizes were also essential to explore the detailed phylogenetic relationships of these taxa. In this study, two complete mitogenomic sequences were sequenced from Phaesticus moniliantennatus (formerly Flatocerus daqingshanensis and F. nankunshanensis). The mitogenome sequences were assembled, annotated and analyzed. The length of the mitogenomes was 16,147 and 16,224 bp, and the nucleotide composition was A>T>C>G, A-skew and C-skew. Large intergenic regions between trnS(ucn) and ND1 were identified with a length of 191-233 bp. Phylogenetic analyses showed that Batrachideinae formed the basal position of Tetrigoidea, followed by Tripetalocerinae. The monophyly of several subfamilies was not supported. Within Tetriginae, P. moniliantennatus clustered with a clade containing Systolederus spicupennis, S. hainanensis and S. zhengi (Metrodorinae), indicating their closer phylogenetic relationship. The divergence time results indicated that Batrachideinae diverged at 170.96 Ma and Tripetalocerinae diverged at 149.36 Ma. And the divergence time between P. moniliantennatus and the closely related Systolederus clade was 87.06 Ma. These results represent the available mitogenome sequences of the genus Phaesticus and provide a valuable data resource for reconstructing phylogenetic relationships and studying the differentiation of Tetrigoidea species.