Mitochondrial Genomes of Two Pygmy Grasshoppers (Orthoptera: Tetrigoidea) and a Comparative Analysis of Caelifera Mitogenomes

First mitogenomic characterization of Macromotettixoides (Orthoptera, Tetrigidae), with the descriptions of two new species

Classification of species is commonly based on morphological, molecular, and distribution depending on the taxa. Macromotettixoides Zheng, Wei & Jiang, 2005 and Formosatettix Tinkham, 1937 are both wingless types of Tetrigidae with extremely similar morphological characteristics, and in the current taxonomic system they are placed in two different subfamilies, Metrodorinae and Tetriginae, respectively. It is difficult to clearly identify the species of these two genera by morphological characteristics, and molecular data is often needed to assist identification. Here, the complete mitogenomes of two new species were sequenced and assembled, with that of Macromotettixoidesorthomargina. Molecular data of species of Formosatettix were used to test the monophyly of Macromotettixoides and to re-assess the generic characters, and also to test whether Macromotettixoides belongs to the Asian Metrodorinae or Tetriginae. Furthermore, mitochondrial characteristics were analyzed and the phylogeny of the Tetrigidae reconstructed based on mitochondrial protein-coding genes (PCGs). The results indicated that the two new species were clustered with Macromotettixoides rather than Formosatettix, and the anterior margin of the fastigium and pronotum of the two new species usually had the humeral angle different from that of Formosatettix. Therefore, after integrating morphological and molecular data, the two new species were placed in the genus Macromotettixoides, M.maoershanensissp. nov. and M.brachycornasp. nov. Finally, a phylogenetic reconstruction supported Macromotettixoides being assigned to Tetriginae rather than Metrodorinae, in contrast to the previous classification of this genus.

Mitochondrial genomes of eight Scelimeninae species (Orthoptera) and their phylogenetic implications within Tetrigoidea

Scelimeninae is a key member of the pygmy grasshopper community, and an important ecological indicator. No mitochondrial genomes of Scelimeninae have been reported to date, and the monophyly of Scelimeninae and its phylogenetic relationship within Tetrigidae is still unclear. We sequenced and analyzed eight nearly complete mitochondrial genomes representing eight genera of Scelimeninae. These mitogenomes ranged in size from 13,112 to 16,380 bp and the order of tRNA genes between COII and ATP8 was reversed compared with the ancestral order of insects. The protein-coding genes (PCGs) of tetrigid species mainly with the typical ATN codons and most terminated with complete (TAA or TAG) stop codons. Analyses of pairwise genetic distances showed that ATP8 was the least conserved gene within Tetrigidae, while COI was the most conserved. The longest intergenic spacer (IGS) region in the mitogenomes was always found between tRNASer(UCN) and ND1. Additionally, tandem repeat units were identified in the longest IGS of three mitogenomes. Maximum likelihood (ML) and Bayesian Inference (BI) analyses based on the two datasets supported the monophyly of Tetriginae. Scelimeninae was classified as a non-monophyletic subfamily.