what is DNA barcoding?
Only a small fraction of species found on Earth are described
Almost 10 million species are estimated to exist on Earth. Despite a history of efforts to identify species that spans over 250 years, the number of species described thus far is fewer than 2 million. Especially taxonomic work on many more challenging groups of species is far from being finished. In many cases, morphology-based species identification is difficult or even impossible. Knowledge about the biodiversity is particularly important now that it is threatened. Many species are in danger to go extinct before they are even discovered.
DNA based species identification
The idea of species identification based on DNA characteristics was introduced in 2003 (Hebert et al. 2003). DNA determines the hereditary characteristics of individuals and gives each species a unique DNA composition. The idea of DNA based species identification states that fast and objective identification is possible if a genomic region that shows low variation within a species, but great variation between species is found. The idea is comparable to the barcodes used in industry, where different items such as grocery products can be identified automatically and unambiguously with a scanner at a store’s checkout counter. Researchers have found the cytochrome c oxidase (COI or cox1) region in mitochondrial genome to be suitable for effectively discriminate species from each other in many organism groups. COI-gene is not applicable to the identification of fungi and plants. In fungi, the chosen DNA barcode is the nuclear ITS region. In plants, a combination of two chloroplast gene regions (matK and rbcL) and increasingly also the ITS region, is used for DNA barcoding.
DNA barcodes are efficient also in the discovery and discrimination of so-called cryptic species, those that closely resemble each other but are biologically distinct species. Using DNA barcodes, it has been demonstrated that, for instance, some groups of parasitic wasp species likely include dozens of species specialized to different host species and which cannot be distinguished morphologically.
Vast amount of taxonomical research and species identification is conducted worldwide. Some researchers have strongly opposed the idea of DNA barcoding, but more and more researchers acknowledge its usefulness. DNA barcodes enable much faster and more reliable identification and discovery of new species than ever before. Since most of the species are still undescribed, increasing the effectiveness of taxonomical research is crucial.