Mitochondrial genomes of Nemourinae species (Plecoptera: Nemouridae) and the phylogenetic implications

Currently, the classification system of 2 subfamilies within Nemouridae has been widely accepted. However, monophyly of 2 subfamilies has not been well supported by molecular evidence. To date, only mitogenomes from genus Nemoura of the subfamily Nemourinae were used in previous phylogenetic studies and produced conflicting results with morphological studies. Herein, we analyzed mitogenomes of 3 Nemourinae species to reveal their mitogenomic characteristics and to examine genus-level classification among Nemouridae. In this study, the genome organization of 3 mitogenomes is highly conserved in gene order, nucleotide composition, codon usage, and amino acid composition. In 3 Nemourinae species, there is a high variation in nucleotide diversity among the 13 protein-coding genes (PCGs). The Ka/Ks values for all PCGs were far lower than 1, indicating that these genes were evolving under purifying selection. The phylogenetic analyses highly support Nemurella as the sister group to Ostrocerca. Meanwhile, Nemoura is recovered as the sister group of Malenka; they are grouped with other Amphinemurinae and emerged from a paraphyletic Nemourinae. More molecular data from different taxonomic groups are needed to understand stoneflies phylogeny and evolution.