DNA Barcoding in Forensic Vertebrate Species Identification

Abstract

Animal identification is essential in a large number of forensic cases, including bush meat harvest, unregulated trade in protected species or species’ derivatives, introduction of exotic species without a proper permit and food fraud. The analysis of morphological traits has been the most traditional method used for species identification and taxonomy. However, when morphological identification is compromised, genetic identification can be used to associate sequences from unknown samples to a sequence from a reference sample. Based on a standard region of 650 base pairs of the subunit I of cytochrome c oxidase mitochondrial gene (COI) and using a validated reference database, the DNA Barcoding system for cataloging and identifying animal species has been proposed. In order to test the utility of DNA Barcoding in forensic vertebrate species identification, COI sequences from previously identified samples from human and a variety of domestic and wild specimens of Brazilian mammals, birds, fishes were compared against the Barcode of Life Database (BOLD). BOLD provided a correct species-level identification for 12 out of the 20 queried sequences (60%) and presented the correct species as the best matched one for 17 out of 18 samples morphologically identified to this level (94%). Cases where BOLD did not deliver a species level identification were associated with the controversial taxonomic status of some species, the possible occurrence of a biological event like hybridization and the lack of representation of some groups in the database. The results showed that DNA Barcoding is already effective for species identification in many cases and, although presenting some limitations, the use of the tool must be improved and widespread in forensic casework.