Phylogeny of the Coleoptera based on mitochondrial cytochrome oxidase I sequence data

A 400 base pair region of the mitochondrial cytochrome oxidase I gene (COI) was sequenced for thirty-seven species of beetle, representing fifteen families. The sequence was found to be highly variable, with 12-18% divergence within families, and up to 27% divergence between families. Phylogenetic analysis using the neighbour-joining method shows the Carabidae (Adephaga) as a distinct clade, but also shows that all other beetles (Polyphaga) diverged soon after the Adephaga/Polyphaga split. Whilst some species are grouped within their respective families, others are too diverged for easy resolution. The main disagreement with trees constructed using comparative morphology and the fossil record is the position of the Coccinellidae. Whilst COI may be an informative gene for molecular systematics at lower taxonomic levels, or in other insects, improved resolution of this particular phylogeny will require a more highly conserved sequence.