Identification of Birds through DNA Barcodes

TLDR

DNA barcodes derived from short standardized genomic regions, such as the 648‑bp COI gene, have emerged as a promising tool for species identification across animals. The study aimed to build a public library of COI barcodes and test their effectiveness in discriminating bird species. The authors sequenced the COI gene for 260 North American bird species and compared the resulting barcodes to assess species discrimination. COI barcodes distinguished all 260 bird species, with interspecies differences averaging 18× larger than intraspecies differences, revealing four potential new species and supporting a 10× threshold for rapid species discovery.

Abstract

Short DNA sequences from a standardized region of the genome provide a DNA barcode for identifying species. Compiling a public library of DNA barcodes linked to named specimens could provide a new master key for identifying species, one whose power will rise with increased taxon coverage and with faster, cheaper sequencing. Recent work suggests that sequence diversity in a 648-bp region of the mitochondrial gene, cytochrome c oxidase I (COI), might serve as a DNA barcode for the identification of animal species. This study tested the effectiveness of a COI barcode in discriminating bird species, one of the largest and best-studied vertebrate groups. We determined COI barcodes for 260 species of North American birds and found that distinguishing species was generally straightforward. All species had a different COI barcode(s), and the differences between closely related species were, on average, 18 times higher than the differences within species. Our results identified four probable new species of North American birds, suggesting that a global survey will lead to the recognition of many additional bird species. The finding of large COI sequence differences between, as compared to small differences within, species confirms the effectiveness of COI barcodes for the identification of bird species. This result plus those from other groups of animals imply that a standard screening threshold of sequence difference (10x average intraspecific difference) could speed the discovery of new animal species. The growing evidence for the effectiveness of DNA barcodes as a basis for species identification supports an international exercise that has recently begun to assemble a comprehensive library of COI sequences linked to named specimens.