The eDNA technique can also be used to generate a complete list of species from a water sample for a specific group of species. For example, we can establish which fish or amphibian species occur in a water body. Universal primers are used to amplify all the DNA of one group in the water sample using PCR. With next generation sequencing (NGS), all amplified pieces of DNA are encoded and stored in a large data file. Those DNA codes are then compared to the DNA codes in our reference database. For each piece of DNA, the computer calculates from which species it originates, thereby generating a list of species.
The costs of the analyzes are higher than with the single species approach. This because of the extra steps involved (sequencing and comparing the data on a computer with the reference database).
There is a trade-off between the number of species you can detect with the primers and the chances of detecting rare species. When the primers aim on too many species, rare species will probably be missed. It is therefore better to aim on one particular group or family.
There are primers for the following groups:
- Telostean Fishes
- Bats (Chiroptera)
- Dragonflies (Odonata)