It can be hard to determine if an animal is extinct or just really good at hiding, especially for already-elusive creatures like frogs. But now, researchers have demonstrated a new way to track lost species by searching for their loose DNA in the environment. Using that method, the team has “rediscovered” several missing frog species in Brazil, including one that hasn’t been seen in over 50 years.
No matter how sneaky a creature is, it won’t be able to help shedding DNA into its environment from skin, fur, hair, scales, feathers, urine, feces and other leavings. This environmental DNA (eDNA) can be tracked and analyzed to give us an idea of what kinds of creatures live in a certain area, even without seeing or catching them directly.
In recent years, eDNA has been used to track fish migration, keep watch for great white sharks and invasive clams and starfish, study which ancient species of humans lived in certain caves, and even figure out that the Loch Ness Monster is probably just a big eel.
And now, researchers from Cornell University have used the technique to track frog species that have been lost to science for decades. The team set out to search for 30 species of amphibians in six areas of the Atlantic Coastal Forest and Cerrado grasslands in Brazil, where they were previously known to live.
First, the researchers trekked into the Brazilian jungle and sampled water from streams and ponds. This was then pumped through filters for catching DNA, which were then sealed for study. Back in the lab, the team extracted the DNA, genetically sequenced it and filtered out material from other animals until only frog DNA was left.
“Now you’ve got a subset of genetic sequences that we know only belong to frogs, and then it’s step by step, going finer and finer, until you get to the genus and species you are looking for,” says Kelly Zamudio, senior author of the study.
Through this, the team found eDNA evidence of seven particularly interesting frog species. The headliner is Megaelosia bocainensis, a species that’s so far only known from a single specimen collected in 1968.
The team also discovered evidence of four species of frogs that were once common but are now rare in the area, as well as two that are found elsewhere but were thought to have vanished from these locations completely.
“Little bits of DNA in the environment don’t tell us about how many individuals there are or whether those individuals are healthy, but it does tell us that the species is still present,” says Zamudio. “This is one more kind of survey data, and for species that are declining or locally disappeared, it not only means they are there, but there’s now the potential to study them in more detail.”
The team hopes to collect more eDNA samples from other areas to try to find more signs of these elusive frogs.
The research was published in the journal Molecular Biology.
Source: Cornell University
