Mitochondrial Genome Architecture of Cephus nigrinus Thomson, 1871 and the Conserved IQM Rearrangement in Cephinae (Hymenoptera: Cephidae)

Mitochondrial gene rearrangements provide useful characters for investigating genome evolution in Hymenoptera, but mitogenomic sampling within Cephidae remains limited. Here, the mitochondrial genome of Cephus nigrinus Thomson, 1871 was reconstructed from publicly available Illumina whole-genome sequencing data (SRA: SRR23907852) and compared with available cephid mitochondrial genomes. The assembled sequence is 16,782 bp long, has an A + T content of 81.38%, and contains 13 protein-coding genes, 22 transfer RNA genes, and two ribosomal RNA genes. An A + T-rich region of 1295 bp was identified in the deposited annotation. Comparative gene-order analysis revealed a conserved rearrangement of the ancestral mitochondrial IQM cluster, characterized by the positioning of trnQ before trnI near nad2 and the relocation of trnM immediately downstream of rrnS. Phylogenetic analyses based on a concatenated dataset of 13 protein-coding genes, 22 tRNAs, and two rRNAs recovered C. nigrinus and C. pygmeus as sister taxa with strong support. However, the placement of this pair relative to C. cinctus received lower support in the maximum-likelihood analysis. The results expand available mitogenomic information for Cephinae and support conservation of the rearranged mitochondrial gene organization among the examined Cephus species. Further validation is needed to establish the complete structure of the repetitive control region.