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Animal diversity can be monitored by collecting DNA from leaves

Since global biodiversity loss is currently accelerating at an unprecedented rate, tracking changes in wildlife is crucial for informing adaptive management strategies and conserving biodiversity. 

Moreover, since the majority of emerging infectious diseases have their origins in wild animal populations, understanding which animal species are where is needed for estimating and potentially reducing the risk of disease spillover into human populations.

Collecting animal DNA 

In a new study published in the journal Current Biology, an international team of scientists has employed a simple yet innovative method of monitoring species compositions in specific regions: sampling DNA from leaves, a technique inspired by recent findings that animal DNA can be sampled from air.

“If animal DNA is in the air all around us, perhaps it settles and gets stuck to sticky surfaces like leaves,” said senior author Jan Gogarten, an expert in the ecology and evolution of infectious diseases at the University of Greifswald

“The rainforest and its plants are often called ‘the lungs of the planet.’ Could the lungs of the planet represent the ideal place to sample settling DNA from air?”

How the research was conducted 

The researchers tested this idea in the Kibale National Park in Uganda, which is well known for its rich biodiversity and has attracted biologists for decades. 

Armed with 24 cotton buds, the scientists started swabbing leaves for three minutes with each of them, aiming to collect samples from as many leaves as possible within the timeframe.

“To be honest, we did not expect great results,” said lead author Christina Lynggaard, a molecular ecologist at the University of Copenhagen. “The rainforest is hot and humid and these are conditions that cause DNA to quickly degrade.”

What the researchers discovered 

However, when the results came back from the DNA sequencer, the researchers were amazed. “We found DNA from an absolutely staggering diversity of animals in those 24 cotton buds – over 50 species of mammals and birds and a frog. And all from just a total of 72 minutes of swabbing leaves,” Gogarten reported.

The analysis detected an average of nearly eight animal species in each of the cotton buds, spanning a wide diversity of mammals and birds from the massive African elephant to a tiny species of songbird. 

Some of the animals that were detected included the hammer-headed fruit bat, an amazing creature with a wingspan of nearly a meter, various species of monkeys such as the elusive L’Hoest’s monkey and the endangered ashy red colobus, as well as a diversity of rodents such as the forest giant squirrel, and birds like the great blue turaco and the endangered grey parrot.

Wildlife management strategies 

“This diversity of detected animals and the high animal detection rate per swab showcase that animal DNA can be readily sampled from leaves,” Gogarten said. “The high detection rate and the ease of sampling can make swabbing a new tool with which to inform wildlife management strategies.”

Currently, animals worldwide are facing significant threats from human activities, leading to severe biodiversity loss, particularly in tropical regions. This worrisome trend has far-reaching consequences for the essential services and functions these ecosystems provide, such as seed dispersal or pollination. 

Thus, careful monitoring of animal populations is crucial for understanding the scale of recent ecosystem changes and for guiding the development of effective management strategies.

Moreover, knowing the location of various animal species is crucial for assessing the risk of spillover in areas where wildlife can get into contact with humans.

Study implications 

“With numerous factors rapidly changing on our planet, understanding how they influence wild animal populations is a complex yet critical task, and we anticipate that DNA detected with leaf swabs can provide us valuable insights,” Gogarten said. 

“We know that many animals live in these dense rainforests, but we rarely see them, and their changing distributions are really difficult to map. This remarkably straightforward sampling method gives us an efficient tool to make the unseeable seeable.”

“Leaf swabbing itself does not require fancy and expensive equipment or lengthy training to carry out, and so it can easily be carried out by citizen science programs. During the COVID-19 pandemic, testing required automated extraction of nucleic acids from millions of swabs per day, and the analytical devices were spread to every corner of the planet. What if these instruments could be repurposed for using swabs to monitor animals on a massive scale?” Lynggaard concluded.

By Andrei Ionescu, Staff Writer

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