In a groundbreaking study, scientists have discovered that frogs can quickly increase their tolerance to pesticides.
While much research has focused on pests evolving resistance to pesticides, there has been less attention on how other animals might adapt similarly. This new study begins to fill that gap.
Rick Relyea, Ph.D., a professor at Rensselaer Polytechnic Institute, led the research team.
Their findings were published in the journal Aquatic Toxicology.
“Most pesticide research targets pests due to economic interests,” Relyea explained. “But we haven’t paid much attention to non-target species, which make up most of the world’s biodiversity.”
The team investigated whether frogs could rapidly develop pesticide tolerance. Traditional toxicology tests determine the lethal amount of pesticide in one exposure. However, Relyea’s team exposed wood frogs to small, non-lethal doses first. This approach allowed many frogs to develop higher tolerance levels within just a few days.
“In the real world, animals are exposed to small doses of pesticides near agriculture, lawns, and landscaping,” Relyea said. “Our research found that wood frogs could increase their tolerance to several common insecticides within days.”
The team studied 15 populations of wood frogs from western Pennsylvania and eastern New York. They tested the frogs’ tolerance to three common insecticides: carbaryl, chlorpyrifos, and diazinon. They compared frogs exposed to no pesticide with those exposed to sublethal doses before facing lethal concentrations. Nearly half of the frog populations showed rapidly increased tolerance.
“We think this rapid increase in tolerance might help animals evolve pesticide resistance over many generations,” Relyea said. “If a population first develops tolerance through sublethal exposure, this tolerance can be genetically favored, helping future generations survive.”
However, this increased tolerance has its limits. “We don’t want people to think pesticides are harmless to non-target animals,” said Jessica Hua, Ph.D., an associate professor at the University of Wisconsin-Madison. “More tolerance doesn’t mean being immune. Pesticides can still be deadly. Moreover, this increased tolerance can come with costs, such as reduced ability to handle other threats like diseases.”
This research is a starting point for further studies. “We hope this opens the door for more research,” said Jason Hoverman, Ph.D., a professor at Purdue University. “Can other amphibians develop pesticide tolerance? Can other animals? Can other pesticides trigger this tolerance?”
Curt Breneman, Ph.D., dean of Rensselaer’s School of Science, praised the study. “Dr. Relyea and his team have shown how amphibians can rapidly adapt to environmental threats and pass this adaptation to future generations. I look forward to seeing more results from this research as we find ways to reduce environmental toxins.”
In addition to Hua and Hoverman, the research team included Devin K. Jones from Purdue University, Devin G. DiGiacopo from Binghamton University, and Rensselaer technicians Brian Mattes and Erika Yates.
