The Complete Mitochondrial Genome of Coptotettix longtanensis and its Implications for the Comparative Analysis and Phylogeny of Tetriginae

Abstract

Mitochondrial genomes are powerful molecular markers for investigating phylogenetic relationships and evolutionary dynamics among closely related taxa. In this study, we sequenced and analyzed the complete mitochondrial genome of Coptotettix longtanensis for the first time. The circular mitogenome is 16,861 bp in length and encodes the typical set of 37 genes, including 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), and two ribosomal RNAs (rRNAs), as well as a non-coding A+T-rich control region. The overall A+T content is 74.82%, exhibiting a strong bias consistent with other members of Tetriginae. The gene arrangement is identical to the ancestral insect pattern, except for a trnK–trnD translocation. Codon usage analysis revealed a clear preference for A- and T-ending codons, and the Ka/Ks ratios of all 13 PCGs were below 1, indicating strong purifying selection. Phylogenetic relationships among 17 Tetriginae species and two outgroups were reconstructed using Bayesian inference (BI) and maximum likelihood (ML) methods based on concatenated PCGs. Our results showed that the two Coptotettix species, C. longtanensis and C. longjiangensis, formed a distinct and well-supported clade, thus clarifying the phylogenetic position of C. longtanensis within Tetriginae. This analysis enhances our understanding of the mitogenome characteristics of Tetriginae grasshoppers and provides a foundation for future phylogenetic research on the family Tetrigidae.