DNA barcoding

Definition

A molecular identification method that uses a short, standardized DNA sequence from a specific gene or genomic region to identify specimens to species by comparison against a curated reference database. In arthropod systematics, the mitochondrial cytochrome c oxidase subunit I (COI) gene serves as the primary barcode marker for animals, though nuclear regions and alternative markers are employed for groups where COI evolution is problematic (e.g., certain Diptera, Cnidaria, or plants). The technique enables identification of fragmentary, immature, or morphologically cryptic specimens, supports rapid biodiversity inventories, and provides an independent dataset for testing species boundaries established through traditional taxonomy.

Etymology

From the parallel with commercial product barcodes: a short, unique identifier scanned against a reference database to retrieve associated information.

Example

A field-collected caterpillar lacking diagnostic adult characters can be identified to species by sequencing its COI barcode and matching it against the Barcode of Life Data System (BOLD), revealing it to be a cryptic species of Noctuidae previously indistinguishable from congeners by larval morphology alone.

Synonyms

• molecular barcoding
• genetic barcoding

Related Terms

• cytochrome oxidase I
• molecular systematics
• cryptic species
• BOLD
• DNA taxonomy
• metabarcoding
• species delimitation
• voucher specimen

Usage Notes

Strictly speaking, DNA barcoding refers to standardized, single-locus identification, whereas DNA taxonomy involves using sequence data to formally describe species. The approach is most powerful when integrated with morphological study and anchored by expertly identified voucher specimens; barcode-only identifications carry risk when reference databases contain misidentified or contaminated entries. Metabarcoding extends the concept to bulk environmental samples, recovering multiple taxa simultaneously without individual specimen handling.