Animals leave traces of their DNA in the soil, water and sediment. Environmental DNA (eDNA) takes samples from the environment to detect the presence of a species without necessary seeing the species in the habitat. For instance, even if we don’t see or hear a specific species of frog, we can still identify the genetic sample left behind in a pond.
With increasing declines reported worldwide, conservationists struggle to keep pace with the rate of amphibians disappearing.
In the past years, scientists have advanced the use of this tool. They are using the method to estimate population sizes, confirm species presence in challenging field conditions, and rediscover species thought to be extinct. Additionally, eDNA method is extremely sensitive and works wonders for rare and cryptic frogs. For these reasons, it is rapidly becoming a standardized sampling approach for amphibians.
In a recent study published in the journal Molecular Ecology by Lopes-etal-2020, researchers looked at 30 targeted amphibians from the Atlantic Forest of Brazil. These species are under different levels of threats, some are declining and others are presumed to be extinct. Firstly, in the field, they sampled 60 L of water from streams and ponds. Secondly, the field team passes the water through a filter to capture the DNA. Finally, the hard work happens in the lab where they extract, sequence, and isolate the DNA to match a specific frog.
With the use of eDNA, researchers successfully detected DNA of four declining species and two locally missing frogs. Also, they rediscovered one species, last seen in 1968!
The method confirms the presence of species that would missed by traditional methods, such as visual surveys. Moreover, researchers are improving its use when small sample sizes are available, like from water retained by the tanks on bromeliads. As eDNA method advances, it has great potential to monitor amphibian population at low densities. It also has a promising use in megadiverse tropical countries, such as Brazil.
Brazil is the most biodiverse country on Earth and is home to hundreds of animals and thousands of plants found nowhere else. Unfortunately, the Atlantic Forest has suffered greater destruction over the past century. Only 12% of its original range persists in Brazil. We work to protect tropical forests across our rewilding sites, including in Brazil. You can read more about our work in Brazil here Rewild our forest.
Watch this space for more news on eDNA and amphibians. We are working on advancing the use of this tool for rare and cryptic bromeliad-dwelling frogs from Brazil!