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The complete mitochondrial genome of Xystrocera globosa is 15,706 bp in length, containing 13 protein-coding genes, 22 transfer RNAs, two ribosomal RNAs and the A + T-rich region. The overall base composition is 72.7% AT and 27.3% GC, and the AT content of the control region is 79.3%. In ML and BI phylogenetic trees, X. globosa was a sister clade to X. grayii. The monophyly of Lamiinae and Prioninae were supported in ML analyses, but nevertheless, the monophyly of Cerambycinae was not recovered.

Cerambycidae is one of the most diversified groups within Coleoptera and includes nearly 35,000 known species. The relationships at the subfamily level within Cerambycidae have not been convincingly demonstrated and the gene rearrangement of mitochondrial genomes in Cerambycidae remains unclear due to the low numbers of sequenced mitogenomes. In the present study, we determined five complete mitogenomes of Cerambycidae and investigated the phylogenetic relationship among the subfamilies of Cerambycidae based on mitogenomes. The mitogenomic arrangement of all five species was identical to the ancestral Cerambycidae type without gene rearrangement. Remarkably, however, two large intergenic spacers were detected in the mitogenome of Pterolophia sp. ZJY-2019. The origins of these intergenic spacers could be explained by the slipped-strand mispairing and duplication/random loss models. A conserved motif was found between trnS2 and nad1 gene, which was proposed to be a binding site of a transcription termination peptide. Also, tandem repeat units were identified in the A + T-rich region of all five mitogenomes. The monophyly of Lamiinae and Prioninae was strongly supported by both MrBayes and RAxML analyses based on nucleotide datasets, whereas the Cerambycinae and Lepturinae were recovered as non-monophyletic.

We determined the mitochondrial gene sequence of Monochamus alternatus and three other mitogenomes of Lamiinae (Insect: Coleoptera: Cerambycidae) belonging to three genera (Aulaconotus, Apriona and Paraglenea) to enrich the mitochondrial genome database of Lamiinae and further explore the phylogenetic relationships within the subfamily. Phylogenetic trees of the Lamiinae were built using the Bayesian inference (BI) and maximum likelihood (ML) methods and the monophyly of Monochamus, Anoplophora, and Batocera genera was supported. Anoplophora chinensis, An. glabripennis and Aristobia reticulator were closely related, suggesting they may also be potential vectors for the transmission of the pine wood pathogenic nematode (Bursaphelenchus xylophilus) in addition to M. alternatus, a well-known vector of pine wilt disease. There is a special symbiotic relationship between M. alternatus and Bursaphelenchus xylophilus. As the native sympatric sibling species of B. xylophilus, B. mucronatus also has a specific relationship that is often overlooked. The analysis of mitochondrial gene expression aimed to explore the effect of B. mucronatus on the energy metabolism of the respiratory chain of M. alternatus adults. Using RT-qPCR, we determined and analyzed the expression of eight mitochondrial protein-coding genes (COI, COII, COIII, ND1, ND4, ND5, ATP6, and Cty b) between M. alternatus infected by B. mucronatus and M. alternatus without the nematode. Expression of all the eight mitochondrial genes were up-regulated, particularly the ND4 and ND5 gene, which were up-regulated by 4–5-fold (p < 0.01). Since longicorn beetles have immune responses to nematodes, we believe that their relationship should not be viewed as symbiotic, but classed as parasitic.

The phylogenetic relationship of Caenidae remains hotly debated within the Ephemeroptera. We sequenced the complete mitochondrial genome of Caenis sp. (Ephemeroptera: Caenidae) to discuss the phylogenetic relationships among the Caenidae. The mitochondrial genome of Caenis sp. collected from Jian’ou, Fujian province, China is a circular molecule of 15,392 bp in length containing 37 genes (13 protein-coding genes, 22 tRNAs, and two rRNAs), which showed the typical insect mitochondrial gene arrangement. In BI and ML phylogenetic trees using 23 species from 13 families, the monophyly of the families Caenidae, Heptageniidae, Isonychiidae, and Vietnamellidae was strongly supported. The clade of Caenidae is a sister clade to the clade of Teloganodidae and Baetidae.