Monarch Butterflies Thrive on Poisonous Milkweed

(p. D5) The caterpillar of the monarch butterfly eats only milkweed, a poisonous plant that should kill it. The caterpillars thrive on the plant, even storing its toxins in their bodies as a defense against hungry birds.

For decades, scientists have marveled at this adaptation. On Thursday [Oct. 3, 2019 [sic]), a team of researchers announced they had pinpointed the key evolutionary steps that led to it.

Only three genetic mutations were necessary to turn the butterflies from vulnerable to resistant, the researchers reported in the journal Nature. They were able to introduce these mutations into fruit flies, and suddenly they were able to eat milkweed, too.

Biologists hailed it as a tour-de-force that harnessed gene-editing technology to unscramble a series of mutations evolving in some species and then test them in yet another.

“The gold standard is to directly test mutations in the organism,” said Joseph W. Thornton, an evolutionary biologist at the University of Chicago. The new study “finally elevates our standards.”

For the full story see:

Carl Zimmer. “MATTER; How Monarch Butterflies Evolved to Eat Poison.” The New York Times (Tuesday, October 8, 2019 [sic]): D5.

(Note: bracketed date added.)

(Note: the online version of the story was updated Oct. 3, 2019 [sic], and has the title “MATTER; These Butterflies Evolved to Eat Poison. How Could That Have Happened?”)

The article in Nature mentioned above is:

Karageorgi, Marianthi, Simon C. Groen, Fidan Sumbul, Julianne N. Pelaez, Kirsten I. Verster, Jessica M. Aguilar, Amy P. Hastings, Susan L. Bernstein, Teruyuki Matsunaga, Michael Astourian, Geno Guerra, Felix Rico, Susanne Dobler, Anurag A. Agrawal, and Noah K. Whiteman. “Genome Editing Retraces the Evolution of Toxin Resistance in the Monarch Butterfly.” Nature 574, no. 7778 (Oct. 2019): 409–12.

The “corresponding author” (often considered the primary author) of the article is Noah K. Whiteman, who has published a book that extensively discusses cases such as the monarch butterfly, where a creature has evolved the ability to consume or make use of chemicals that are poisonous to other creatures:

Whiteman, Noah. Most Delicious Poison: The Story of Nature’s Toxins―from Spices to Vices. New York: Little, Brown Spark, 2023.

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