Comparative Analysis of the Mitochondrial Genomes of Three Species of Elmidae (Coleoptera: Dryopoidea)

The mitochondrial genomes of three species of Elmidae were sequenced. The sizes were 16,309 bp (<i>C. jaechi</i>), 16,291 bp (<i>G. longiusculus</i>), and 15,480 bp (<i>S. punctulata</i>). Each genome includes 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs), and a control region (CR). All three mitogenomes show AT bias. Except for <i>trnS1</i>, lacking the dihydrouridine (DHU) arm, all tRNA genes had a typical cloverleaf structure. The codon usage preferences of the three species showed high similarity. The arrangement of the genes in the three mitogenomes was consistent among them but differed from that in the typical mitogenomes of Coleoptera. The Ka/Ks ratio indicated that <i>COX1</i> and <i>nad4L</i> had a lower evolutionary rate, being relatively conserved genes among 13 PCGs. The phylogenetic analysis revealed that Elmidae belongs to the superfamily Dryopoidea within the suborder Polyphaga and is monophyletic. The results preliminarily indicate that the taxonomic groups at the subfamily, tribe, and genus levels within Elmidae are ambiguous, and further revisions may be required in the future.