But for many biologists, tracking mammals that move miles a day and keeping an eye on humans is nearly impossible. enter eDNA. “If we want to restore ecosystems, we need to understand how our conservation actions affect endangered and endangered species. But to do that, we need to be able to spot even the rarest, most timid and most obscure species,” said Michael Schwartz, senior scientist at the Center for Fish and Wildlife Conservation. National Forest Service in Missoula, Montana, wrote in an email. into WIRE. “We need new technologies, like the ability to detect environmental DNA in the air.”
Schwartz, who was not involved in these two new studies, used air, water and soil samples to track large brown bats (Eptesicus fuscus), whose numbers have been ravaged by white nose syndrome, a fungal disease that arrived in the United States in 2006. Schwartz and his colleagues published a study in September in the journal magazine Biological conservation examined eDNA samples from soil and water outside caves where bats reside. They also used an air sampler as part of a project to see if they could collect airborne DNA from a bat barn in Ohio. The study found that six out of seven filtered air samples successfully detected their eDNA in the air, but at low concentrations, even though 30 bats were housed in the room.
Schwartz says his colleagues are improving their air sampling technique and working on a method of collecting a small amount DNA from snow. This not only allows the USFS team to detect which mammals have recently traveled end snow and ice, but digging in it also allowed them to find evidence that a particular animal had passed through the area months earlier. Schwarz’s team published some of the results on this project in the journal Biological conservation in 2019. Using snow tracks to detect timid predators like lynx is cost-effective, efficient and definitive, he said.
Does airborne DNA sampling work to track genetic material from individuals? One expert said theoretically yes, but practically no. “It’s possible but it’s going to be a bit more difficult,” said Melania Cristescu, an associate professor of ecological genomics at McGill University who uses eDNA to sample aquatic habitats. Human DNA fragments from hair, saliva, blood or other genetic material are left on surfaces easier to analyze than air. (Swiss researchers recently solved a family ancestry mystery using DNA from postage stamps affixed on a postcard from World War I, demonstrating the stability of the molecule under certain conditions.) But it will take longer to obtain a sufficient airborne sample of genetic material large and the researchers would have to be very careful not to allow their own DNA to contaminate the filter.
With DNA in the air, weather is also a factor. For example, sampling may not be effective if it’s raining or windy because these conditions can clear the air of DNA-carrying particles. It is also not clear how well the molecule will retain heat under heat or sunlight. “Does solar radiation degrade DNA? Possibly, but we don’t know what the odds are,” Clare said. “We don’t know how far the wind can disperse DNA. We don’t know how temperature might affect its degradation rate. These are all really interesting questions.”
