DNAbarcode

DNA barcode refers to a short, standardized region of an organism’s genome that can be used to identify species. In animals, the most widely used locus is a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene; in plants, commonly used barcodes include the chloroplast genes rbcL and matK; fungi are often identified using the internal transcribed spacer (ITS) region; bacteria are typically identified using the 16S rRNA gene, though multilocus approaches are also employed. The concept aims to enable rapid, scalable species identification regardless of life stage or morphology by comparing an unknown sample’s barcode sequence to a reference library.

Workflow typically involves extracting DNA, amplifying the barcode region via PCR, sequencing the amplified product, and matching the sequence against a reference database to assign a species label, often through similarity thresholds or phylogenetic methods. DNA barcoding is frequently complemented by metabarcoding or environmental DNA (eDNA) approaches that target community composition from mixed samples.

Applications span biodiversity surveys, ecological monitoring, taxonomic discovery, conservation planning, food authentication, and wildlife forensics. It also supports rapid screening for invasive or threatened species and provenance testing in trade.

Prominent resources include the Barcode of Life Data Systems (BOLD), which hosts curated barcode records and tools, and public repositories such as GenBank. Limitations include dependence on comprehensive, accurate reference libraries; intra-specific variation and introgression; closely related or cryptic species; degraded DNA or sequencing errors; and occasional misidentifications in public records. DNA barcoding is a powerful complement to traditional taxonomy, not a universal replacement.