Sometimes we smell them – but the air can apparently contain even more information about animals: Using traces of DNA from this medium, two research teams were able to independently identify numerous zoo residents. As they explain, they show the potential of this detection method for studies of biodiversity in field research.
Which animal species are where in an ecosystem? Researchers traditionally pursue this question through observations, surveillance cameras or on the basis of legacies and tracks. However, these procedures are associated with intensive work and require the animals to be physically present in a timely manner. Alternative and less complex verification options are therefore in demand. The research teams led by Elizabeth Clare from York University and Kristine Bohmann from the University of Copenhagen therefore decided to explore the extent to which a detection technique can be used that has already revolutionized the monitoring of water ecosystems: the investigation of environmental DNA. “Our two working groups are concerned with developing and applying new processes, so it seems that we came up with the same idea at the same time,” says Clare.
The concept of studying aquatic environmental DNA is based on the analysis of small amounts of genetic material that animals such as fish or amphibians release into the water. The two teams now focused on the question of whether such traces can also be detected in the less load-bearing medium of air. They chose environments with a special biodiversity as the study sites for the two proof-of-concept studies: zoos. The advantage was that the researchers knew exactly where which animals were. “If you use a zoo as a model, for example, the recorded DNA of a tiger can be precisely assigned,” explains Clare.
DNA is in the air
Both research groups conducted their study in a nearby zoo by collecting samples from different locations. They used slightly different methods to do this, but they are ultimately based on the same principle: air is sucked in and blown onto a filter material. Genetic material from various biological sources such as breath, saliva, fur or feces also land on this. “Anything that can get into the air and is small enough to float comes into question,” says co-author Christina Lynggaard from the University of Copenhagen. “After filtering the air, we extracted the DNA and made many copies of the animal DNA using PCR amplification. By sequencing this genetic information, we were then able to compare it with a DNA reference database in order to identify the respective animal species, ”explains Lynggaard.
With their results, the two teams of scientists have now been able to prove that this procedure leads to surprisingly productive results: In fact, many zoo animals and some wild animals from the area were found in the air. Clare’s team identified the DNA of 25 species of mammals and birds at Hamerton Zoological Park in the UK, as well as the genome of wild hedgehogs. Bohmann’s researchers recorded the genetic traces of a total of 49 species of mammals, birds, reptiles, amphibians and even fish at Copenhagen Zoo. This included zoo animals such as the okapi, the armadillo and even genes from guppies in a pond in the tropical house had apparently got into the air. In addition, the team found the signatures of locally occurring animals such as squirrels, brown rats and house mice, as well as food animals in the zoo.
Potential for biodiversity research
The large range of detected species shows that eDNA from the air is suitable for the detection and monitoring of terrestrial animal species in the wild, sum up both research teams. As they report, they knew nothing of each other’s work until they completed their studies. When they finally got in touch, they were thrilled by the parallelism of the experiments and results. Clare and Bohmann agreed that this illustrates the potential of technology. So the two groups decided to submit the manuscripts for simultaneous publication in the journal “Current Biology”.
Now they hope that the concept can establish itself in research. “The non-invasive nature of this approach makes it particularly valuable for observing threatened species. They don’t have to be visible for us to know they are in the area when we can literally pick up traces of their DNA from the air, ”says Clare. “Air samples could revolutionize terrestrial biomonitoring and open up new possibilities for tracking the composition of animal communities and recognizing the invasion of alien species,” says the scientist.
Source: Cell Press, York University, technical article: Current Biology, doi: 10.1016 / j.cub.2021.11.064 and 10.1016 / j.cub.2021.12.014