DNA barcoding is a method of species identification using a short section of DNA from a specific gene or genes.
The premise of DNA barcoding is that, by comparison with a reference library of such DNA sections (also called “sequences”), an individual sequence can be used to uniquely identify an organism to species, in the same way that a supermarket scanner uses the familiar black stripes of the UPC barcode to identify an item in its stock against its reference database.
These “barcodes” are sometimes used in an effort to identify unknown species, parts of an organism, or simply to catalog as many taxa as possible, or to compare with traditional taxonomy in an effort to determine species boundaries.
Applications of DNA Barcoding include:
1. Identification of species: Identification of species listed in the Convention of the International Trade of Endangered Species (CITES) appendixes using barcoding techniques is used in monitoring illegal trade.
2. Detection of invasive species: used to screen ecosystems for invasive species, and to distinguish between an invasive species and native species which are morphologically similar.
3. Delimiting cryptic species: process of delimiting cryptic species using DNA barcodes can be as subjective as any other form of taxonomy. However previously overlooked morphospecies can be detected, increasing the total species richness in the sample.
4. Diet analysis and food web application: DNA metabarcoding can be conducted on stomach contents, feces, saliva or whole body analysis.
5. Barcoding for food safety: The purpose is to guarantee food traceability, to minimize food piracy, and to evaluate local and typical agro-food production.
6. Biomonitoring and ecological assessment: used to assess the presence of endangered species for conservation efforts
When barcoding is used to identify organisms from a sample containing DNA from more than one organism, the term DNA metabarcoding is used, e.g. DNA metabarcoding of diatom communities in rivers and streams, which is used to assess water quality.
1. Physical parameters: The major limitation of the barcoding method is that it relies on barcode reference libraries for the taxonomic identification of the sequences.
2. Technological bias: the risk of contamination of the DNA sample.
3. Lack of standardization: no agreement concerning the methods for DNA preservation or extraction, the choices of DNA markers and primers set.
4. Another criticism of DNA barcoding is its limited efficiency for accurate discrimination below species level.
5. Mismatches between conventional (morphological) and barcode based identification.
Despite the advantages offered by DNA barcoding, it has also been suggested that DNA barcoding is best used as a complement to traditional morphological methods.