Barcoding Biodiversity: DNA Barcodes and Environmental DNA (eDNA)
Definition
DNA Barcodes
DNA barcodes are short, standardized DNA sequences unique to each species, much like product barcodes in a store. These genetic "fingerprints" enable species identification, even from small or incomplete samples.
- Traditional identification of species often depends on morphological features (e.g., flower shape, body markings).
- Many organisms are hard to identify: plants without flowers, insect larvae, or rare animals that leave only traces behind.
- DNA barcoding and environmental DNA (eDNA) provide a modern method for rapid and accurate species identification.
- A feather found in a forest can be analyzed for its DNA.
- By amplifying the CO1 gene using polymerase chain reaction (PCR) and comparing it to a reference database, scientists can identify the bird species, regardless of visual evidence.
Environmental DNA (eDNA)
Definition
Environmental DNA (eDNA)
Environmental DNA (eDNA) refers to genetic material shed by organisms into their surroundings through skin cells, mucus, feces, or other biological materials. It enables species detection without direct observation.
How Does eDNA Work?
Imagine investigating a pond’s biodiversity:
- Sample Collection: Collect water, soil, or air samples from the environment.
- DNA Extraction: Use chemical and physical methods to isolate DNA.
- Amplification: Amplify barcoding regions using PCR to increase detectable DNA.
- Sequencing: Sequence the amplified DNA to read its genetic code.
- Comparison: Match sequences to a reference database to identify species.
- Its advantages are:
- Allowing detection of elusive, nocturnal, or rare species.
- Non-invasive, preserving species and habitats.
DNA Barcodes: The Genetic "Fingerprint"
- DNA barcodes are chosen from genes conserved across species, but which also show enough variation between species.
- Animals: Cytochrome oxidase subunit I (COI) in mitochondrial DNA is widely used.
- Plants: Chloroplast genes rbcL and matK.
- Prokaryotes: 16S ribosomal RNA genes.
