Barcoding animal life: cytochrome <i>c</i> oxidase subunit 1 divergences among closely related species

TLDR

The animal kingdom’s vast diversity and complex life stages make taxonomy difficult, but a DNA-based system using the mitochondrial COI gene has been proposed to help resolve this diversity. This study extends COI‑based species diagnosis to the entire animal kingdom. COI sequence divergences reliably distinguish closely related species in all animal phyla except Cnidaria, due to high mutation rates and limited intraspecific variation driven by selective sweeps involving the nuclear genome.

Abstract

With millions of species and their life-stage transformations, the animal kingdom provides a challenging target for taxonomy. Recent work has suggested that a DNA-based identification system, founded on the mitochondrial gene, cytochrome c oxidase subunit 1 (COI), can aid the resolution of this diversity. While past work has validated the ability of COI sequences to diagnose species in certain taxonomic groups, the present study extends these analyses across the animal kingdom. The results indicate that sequence divergences at COI regularly enable the discrimination of closely allied species in all animal phyla except the Cnidaria. This success in species diagnosis reflects both the high rates of sequence change at COI in most animal groups and constraints on intraspecific mitochondrial DNA divergence arising, at least in part, through selective sweeps mediated via interactions with the nuclear genome.