Mitogenomic characterization of Hoplia bomiensis Zeng (Coleoptera: Scarabaeidae: Melolonthinae) from Xizang, China

The complete mitogenome of Hoplia bomiensis Zeng (H. bomiensis) was sequenced and characterized. It was 16,311 bp in length and exhibited conserved gene order, content, and orientation typical of Scarabaeidae. All protein-coding genes (PCGs) began with ATN start codons. The COX1, COX2, and COX3 genes terminated with incomplete stop codon T, while the remaining PCGs ended with TAA or TAG. The non-synonymous (Ka) to synonymous (Ks) substitution ratios for all 13 PCGs were less than 1, suggesting purifying selection. ATP8 displayed the highest Ka/Ks ratio (0.48) and the largest genetic distance compared to the other PCGs. Sliding window analysis identified ND2 as the most variable gene and COX1 as the most conserved. This mitogenome contained 22 tRNA genes, all exhibiting typical cloverleaf structure except trnS1, which lacked the dihydrouracil (DHU) arm. Codon usage was strongly biased toward A/U-ending codons, particularly UUA, AUU, and UUU. Phylogenetic analysis indicated two clades in the family Scarabaeidae. The first clade contained Aphodiinae and Scarabaeinae. Within the second clade, Sericinae diverged first. Melolonthinae was recovered as a non-monophyletic group with three distinct clades, where H. bomiensis formed a highly divergent lineage and exhibited unstable phylogenetic positions between nucleotide- and amino acid-based trees.