Cytochrome b or cytochrome c oxidase subunit I for mammalian species identification—An answer to the debate

Species identification for forensic purposes is being increasingly used, as the value of non-human evidence is realized. This requires the identification of the species before individual analysis can take place. Traditionally the cytochrome b (cyt b) gene was used for species identification, but in 2003 the cytochrome c oxidase subunit 1 (CO1) gene was introduced under the terminology ‘barcoding’. This started an ongoing debate as to which gene offers the best template for species identification (high inter-species variability and low intra-species variation). Sequence data from 236 mammals were compared with multiple sequence alignments for a large number of human, cow and dog samples. Comparisons were made based on the number of inter-species variations between the different species and the intra-species variation between members of the same species.