UC Berkeley study finds genetic mutations in monarch butterfly predators

Photo of monarch butterflies on a branch
Lincoln Brower/Courtesy
Researchers from UC Riverside and UC Berkeley found that some predators of monarch butterflies evolved to have genetic mutations that allow them to eat milkweed, a plant containing poisonous toxins typically consumed by insects with milkweed toxin-resistant mutations.

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According to a study from UC Riverside and UC Berkeley researchers, some predators of monarch butterflies have evolved through genetic mutations that allow them, too, to eat poisonous milkweed, making butterflies fair game for their food.

Simon Groen, co-author of the study and assistant professor of evolutionary systems biology at UC Riverside, said the study aimed to figure out how natural enemies are attacking butterflies.

Monarch butterflies and other brightly colored insects commonly eat milkweed, which contains toxins poisonous to other species, according to Groen. Two years ago, research from UC Berkeley found these butterflies developed a key genetic mutation that made them resistant to milkweed toxins, allowing them to feast on it freely.

Groen said it was believed that monarch butterflies stored these toxins inside of their bodies, working to deter potential predators.

However, the findings of the study proved otherwise.

“Birds, rodents and other animals seemed to do very well attacking and feeding on monarch butterflies,” Groen said.

To conduct the study, researchers took advantage of projects in recent years that have made the genomes of various groups of animals available, according to Groen.

He said the study focused on analyzing the DNA of four different monarch butterfly predators — a bird, rodent, parasitoid wasp and roundworm.

The researchers discovered these predators had acquired almost identical genetic mechanisms for resisting milkweed toxins as the butterflies and other insects that feed on it.

“Monarch butterflies and other insects evolved a set of changes in sodium pumps that allowed their sodium pumps to become insensitive to cardiac glycosides in milkweed,” Groen said.

These findings, Groen said, allow scientists to gain a deeper understanding of how evolution really works and are an example of how mutations of certain species can have critical effects on the wider food chain.

“Evolution finds the same solution over and over again,” Groen said. “It is very remarkable.”

Looking forward, these findings can be helpful when trying to predict what evolution is going to do in certain situations, Groen said.

For example, it can give researchers insight into how pests will respond to the chemicals in man-made pesticides, as some of these insects have developed resistance to them in the same way they have to milkweed, according to Groen.

Groen is hoping to test the findings of this study and see if they hold true by performing more experiments on roundworms’ sodium pumps.

Contact Lydia Sidhom at [email protected], and follow her on Twitter at @SidhomLydia.