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Lost frogs rediscovered with environmental DNA


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Scientists have detected signs of an extinct and unseen listed frog since 1968, using a novel technique to locate declining and vanished species in two regions of Brazil.

The Frog, Megaelosia bocainensis, was among the total seven species ̵

1; including four other declining species and two that had disappeared locally for many years – that have been detected. The findings appeared in a paper, “Lost and Found: Frogs in a Biodiversity Hotspot Rediscovered with Environmental DNA”, published in August in Molecular ecology.

Megaelosia bocainensis. A species that disappeared from Parque Nacional da Serra da Bocaina, Brazil, known only from this museum specimen collected in 1968 and detected by eDNA surveys. In the study, researchers collected and analyzed environmental DNA (eDNA) in the biodiversity of the Atlantic coastal forest and grasslands. of Cerrado of Brazil.

The eDNA technique offers a method of investigation that can confirm the presence of species not detected by traditional methods, providing a tool for conservation scientists to assess the presence of threatened species, particularly those with low population density and those that do not have seen for years.

After careful research to identify species at varying threat levels in these regions of Brazil, the researchers used the eDNA method to search for 30 target amphibian species in six locations where frogs were known to previously live.

“Small bits of DNA in the environment don’t tell us how many individuals there are or if these individuals are healthy, but it does tell us the species is still present,” said senior author Kelly Zamudio, Goldwin Smith Professor of Ecology and Biology. developmental at the College of Arts and Sciences.

“This is another kind of survey data, and for species that are in decline or disappeared locally, it not only means they are there, but there is now the potential to study them in greater detail,” he said, noting that for many species, very little is known.

Around the world, conservationists have been challenged to keep pace with the decline and disappearance of amphibians. At the same time, living organisms leave traces of DNA in soil, water and air. Now, scientists are increasingly using highly sensitive sampling techniques to detect eDNA for preservation purposes.

In the study, the researchers targeted 13 species of frogs that have completely disappeared and are presumed extinct; 12 frogs that have disappeared locally but are still found in other parts of their range; and five species that were once very abundant and are still there but hard to find.

The researchers entered the sampling sites carrying battery packs, a peristaltic pump the size of a shoebox, and backpacks of sterile tubes. They used the pump and hose to draw up to 60 liters of running or tin water through a capsule equipped with a filter to capture DNA. A buffer was then applied to stabilize and preserve the DNA on the filter.

Back in the lab, the researchers extracted the DNA, genetically sequenced it, eliminated genetic material from humans, pigs, chickens and other organisms until they were able to isolate all of the frog DNA.

“You now have a subset of genetic sequences that we know belong only to frogs, and then it’s step by step, getting finer and finer, until you get to the genus and species you’re looking for,” Zamudio said.

Identification M. bocainensis it required intelligent detective work: the species had disappeared long ago and there were no tissues from which to extract the DNA for comparison with the eDNA. But the researchers had the sequences for all sister species of the genus Megaelosia and knew the ranges of the sister species and M. bocainensis.

“We know there is a Megaelosia there,” said Zamudio, “we just don’t know which one it is, but the only one that has ever been reported historically is the one that has disappeared. Can we believe it? Analysis can lead us.”

Zamudio added that it may be worth collecting samples from nearby areas for further signs M. bocainensis.

Using DNA to search for fish species

More information:
Carla Martins Lopes et al. Lost property: frogs in a rediscovered biodiversity hotspot with environmental DNA, Molecular ecology (2020). DOI: 10.1111 / mec.15594

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Lost frogs rediscovered with environmental DNA (2020, September 8)
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