As a student, Christine Bowman sacrificed herself for her academic pedigree. Bowman struggled to collect genetic clues about the surrounding wildlife by examining the intestines of parasites in a leech-infested stream in Madagascar. To do so, he must first allow them to cling to his naked skin. “I acted as a human prey,” said Bowman, now an associate professor of evolutionary genomics at the University of Copenhagen. “These leeches actually feed on rainforest animals, draw their blood, and are excellent DNA preservatives.”
Bowman and another group of researchers have now found a much simpler way to sample peripheral DNA, or eDNA. They installed several air filters in and around the two zoos to capture microscopic pieces of genetic material floating in the air. After removing small filters and replicating DNA using a sequencer, they were able to find the genetic markers of dozens of captive animal species, as well as surrounding free organisms such as squirrels, cats and hedgehogs.
While scientists are using eDNA-like sampling techniques to identify the genetic material of fish and other organisms in rivers and oceans, this is the first time this technique has been used to collect mammalian DNA from the air. The next step, Bowman says, is to understand how this method can be used in nature and how it can be adapted to different habitats and ecosystems.
The results of these two zoo-based experiments were recently published in the journal Current Biology. The first paper by Bowman’s team at the University of Copenhagen. The second report is from a group of researchers from Queenmury University in London and York University in Toronto.
Danish researchers installed three air filters for 30 hours at a time and were able to identify 49 vertebrates, including 30 mammals, 13 birds, four fish, an amphibian and a reptile. They found the DNA of zoo animals such as the short-necked giraffe (Okapi), the armadillo, the guppy (a species of fish that lived in a pond in a forest house) and even the DNA of annoying animals such as brown rats and mice. Fragments of DNA from fish used to feed other zoo animals also flew into the sky and were trapped and identified by a filter.
Laziness at the Copenhagen Zoo, where Christine Bowman collected air samples
In contrast, the British team sampled the air around Hammurton Zoo near Cambridge. Their sampling time was 30 minutes each time; But they moved the filters from place to place to see if they could track the animals’ movements.
According to Elizabeth Keller, lead researcher and assistant professor of biology at York University, the team collected 72 samples and used a laboratory technique called polymerase chain reaction to amplify small amounts of genetic material to identify the genetic markers of individual species. He says:
The DNA filter works like a coffee strainer: you pass air through it and the particles get stuck in it, just like coffee grounds get stuck in the strainer but the water passes through it quickly. What we want to do is trap DNA or cells or microscopic pieces of tissue in the air on this filter. We can then return to the sterile laboratory, open the tube, remove the filter, and extract the DNA directly from it.
The British team identified 25 species of animals, including 17 captive animals such as gibbons, dingoes, dwarfs, sloths and donkeys. They also found random visitors such as squirrels and a hedgehog who were probably wandering around the park in search of food. In addition to the presence of these animals, the team was able to detect their movement.
Chlorine expects air sampling to be used in science soon. This tool will be important for biologists trying to find endangered animals where they live, reproduce or migrate, and to protect those areas from human development.
Wildlife researchers have been looking for a better way to track animals for years. Some install trap cameras along known wildlife trails to capture images of cautious creatures that may emerge infrequently or at night. Others look for signs of stool that may indicate the presence of the animal and the food it eats. There is also an old method: footprints left by a muddy river, snow or a sandy desert. But for many biologists, it is almost impossible to follow mammals that travel miles every day and are cautious about humans.
Michael Schwartz, senior scientist at the US National Forestry Center for Wildlife Genomics and Conservation, wrote in an email to Wired:
If we are to restore ecosystems, we must understand how our conservation measures affect endangered and endangered species. But to do so, we must be able to identify even the rarest, most cautious, and mysterious species. We need technologies such as the ability to detect peripheral DNA in the air.
Schwartz, who did not participate in the two new studies, used air, water and soil samples to track large brown bats.Eptesicus fuscus) Has been severely reduced due to white nose syndrome. The syndrome is a fungal infection that arrived in the United States in 2006.
Schwartz and colleagues published a study in the journal Biological Conservation in September that examined soil and water eDNA samples outside caves where bats nest. They also used an air sampler as part of the project to see if they could collect airborne DNA from a bat barn in Ohio. According to the study, eDNA was detected in six of the seven filtered air samples, but the concentrations were very low, even though 30 bats were in the area.
Schwartz says his colleagues are refining air sampling techniques and working on a way to collect small amounts of DNA from snow. This method not only allows researchers to identify which species of mammal has recently moved on snowflakes, but digging into it allows them to find evidence that a particular animal passed through the area months ago.
In 2019, the Schwartz Group published the results of this project in the journal Biological Conservation. He says using snowflakes to identify conservative predators like the Lynx is an efficient, cost-effective and definitive way.
Dingoes watch air sampling equipment at the British Zoo.
Is airborne DNA sampling efficient for tracking the genetic material of individuals? Experts say, hypothetically yes, but not in practice. “It may be possible, but it will be a bit challenging,” said Melania Christesco, an associate professor of environmental genomics at McGill University who uses eDNA to sample aquatic habitats.
Analyzing human DNA fragments using samples of hair, saliva, blood, or other genetic material left on the surface is easier than analyzing samples collected from the air. (Recently, Swiss researchers were able to solve the riddle of a family tree using the DNA left on postage stamps left on a postcard from World War I, showing the molecule’s stability under certain conditions.)
But getting enough samples of airborne genetic material takes longer, and researchers need to be careful that their own DNA does not contaminate the genetic material on the filter.
Climate is also a factor in airborne DNA. For example, if the air is rainy or windy, sampling may not be efficient because it can clear the air of DNA-carrying particles. It is also not known how long the molecule lasts under heat or strong sunlight. Clare says:
Do solar radiation damage DNA? Probably, but we do not know the extent of the damage caused by it. We do not know how much wind can scatter DNA. We do not know how temperature can affect DNA damage. These are all interesting questions.
Bowman and Clare say their zoo-based experiments are just the beginning, and they hope research will continue to improve sampling and other techniques.
The whole field of eDNA is evolving rapidly, and scientists predict that in the future we can use this method to detect things like the movement of animal or plant species invading an area. We can also use this approach to determine if a particular piece of forest needs protection because it is used by animals for migration or food.
Researchers say it is important to identify patterns of animal movement over time, rather than just knowing their current position, to protect habitats from developing and conserving the Earth’s biodiversity. Clare says:
Almost everything that exists requires the presence of an animal during your presence. If you have a trap camera, the animal must walk in front of it. If it walks behind it, you will never notice its presence. But DNA is a non-invasive method, as the animal may have been there days ago and you can still identify it. This is more like a footprint left behind.