Scientists have found a way to identify animals that have passed by and have already left or are hiding too well to be found – by sucking their DNA fingerprints in the air.
Environmental DNA or “eDNA” is released by organisms into their environment from dead skin cells or feces. It has already been used to monitor the biodiversity of animals that live in water or soil, from fish to microbes.
Today, biologists and environmentalists are excited to invent a way to use eDNA in the air to monitor terrestrial animals such as birds and mammals, especially vulnerable species.
“It’s just mind-boggling,” said Jennifer Sunday, assistant professor of ecology and evolution at McGIll University. She was not involved in the study, but uses eDNA to study the biodiversity of aquatic species.
The technique was developed independently by two groups of researchers, one led by Kristine Bohmann, associate professor of evolutionary genomics at the Globe Institute at the University of Copenhagen and the other by Elizabeth Clare, who is now at York University. in Toronto.
“If you are working with a critically endangered or very rare population that is very sensitive, you may never see them in the environment, even though you know they are there,” Clare said.
“Or alternatively, you might not be able to get close to them because they are so sensitive or so protected.”
With eDNA detection, she said, the animal doesn’t need to be physically present. He might have been gone awhile ago. “And so when you’re looking for something rare, that’s a big plus.”
Two scientific papers describing how animals can be detected from DNA in the air, one by Claire and her collaborators and the another from Bohmann and his team were published this week in the journal Current Biology.
How it works
Clare started by testing the air in her lab, which at the time was at Queen Mary’s University in London, UK, where she was a lecturer. The lab housed a colony of animals called hairless mole rats.
She and her team installed a vacuum pump that would suck air through a piece of filter paper – similar to that used to brew coffee – in her lab. The next step was to extract any DNA that might be on the paper and make additional copies of it using a technique called PCR, which is also used in COVID-19 tests, so that it could be more easily detected and analyzed. The DNA was then compared to known databases of different species.
“To our delight and probably our surprise, every sample we took contained DNA,” she recalls. “We had naked mole rat DNA. We had human DNA. We had dog DNA.”
The last one was a surprise and a puzzle, as there were no dogs in the lab – until the team realized that one of the animal care technicians had taken care of the her mother’s dog on weekends and probably brought her DNA into the lab somehow. on his clothes.
“And so suddenly we realized that not only was it going to work – it was actually much more sensitive than expected,” said Clare, whose research was funded by the Engineering and Physical Sciences Research Council in the UK.
What happened next – at the zoo
Clare decided the next step was to try an environment that was less controlled, but one where researchers could clearly identify the source of the DNA and how far away it was.
So they went to Hamerton Zoo Park in England and collected more than 70 air samples from different locations, indoors and outdoors.
The researchers managed to detect the closest animals, but also some that were hundreds of meters away.
“We found dingo DNA in the gibbon enclosure and we found zebra finch DNA in the primate house,” Clare said.
That’s not all. They have also detected DNA from chicken and beef in animal feed, and local wildlife such as squirrels and even the European hedgehog, a critically endangered species that zoo staff have confirmed. having spotted wandering in the park.
“There’s something that we really, really want to be able to detect with this kind of technology, because they need more biomonitoring of rare species,” Clare said. “So I think that was probably our most exciting detection.”
Scientific minds think the same
As the team prepared to release their study on the zoo, some reporters covering their previous lab work asked if they could see it. Clare obliges her to publish it as a preprint online before publication.
Two days later, she received a flurry of text messages from her research team – another group of scientists from Denmark had seen the article and published their own paper presenting a very similar experiment at the Copenhagen Zoo, funded by a foundation. philanthropic called the Villum Fonden which supports scientific and technical research.
This team, led by Bohmann, used another water-based commercial vacuum cleaner and collected air samples at three different locations.
“In just 40 samples, we detected 49 species spanning mammals, birds, amphibians, reptiles and fish. In the Rainforest House, we even detected the guppies in the pond, the two-toed sloth and the boa, ”Bohmann said in a press release.
She and Clare got in touch and decided to submit their two papers to the same journal for publication at the same time, arguing that it was a great idea as it showed independent scientific replication. It was something they had never heard of from someone who had tried it before, but it worked.
How it could become a valuable conservation tool
Clare said the next step in the research is to determine how long DNA stays in the air and what environmental conditions are causing it to build up or break down.
In the future, she hopes the technique will be a valuable tool not only for rare species, but as an early warning system for invasive species or a tool to detect species in hard-to-reach places such as caves. or burrows.
She said eDNA is already commonly used as a tool by regulators to monitor biodiversity and populations in aquatic environments. Likewise, she hopes the eDNA from the air will become just as valuable.
When asked if DNA from the air could potentially be used in forensic crime investigations, Clare replied, “I guess theoretically. But she noted that the DNA analysis procedure would be quite different from theirs, which aims to differentiate between species.
Canadian researchers using eDNA as a biomonitoring tool for marine and aquatic conservation have been excited about the development.
“I’m actually very happy to read this article,” said Mehrdad Hajibabaei, associate professor at the Center for Biodiversity Genomics at the University of Guelph.
Hajibabaei, who is also the founder of eDNAtec, a consultancy that provides eDNA-based ecological and biological monitoring to clients such as offshore energy and fisheries, called it a “milestone” that has the potential to monitor species such as top predators which are rare, elusive, and roam across huge territories.
What he hopes to see next is if it can be scaled up, and in natural environments, and developed into a tool that can be used by groups such as regulators, as Clare has suggested.
Jennifer Sunday, of McGill University, said she found it amazing that the technique seemed to work.
She said traditional methods of tracking biodiversity, such as trapping, photographing or listening for species, are difficult and laborious.
One of his research areas is to follow how the distribution of species changes with human-caused climate change. It’s very difficult.
“And so one of the reasons to be excited about eDNA technology is that it can transform the way we track changes in biodiversity on a much larger scale. [and] faster to make it more like a weather tracker, ”Sunday said.
“And that’s going to totally change if we do it and if we do it well. I think we could be a lot more proactive and [gain a better] comprehension.”
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