- Author: Kathy Keatley Garvey
Whiteman, UC Berkeley professor of genetics, genomics, evolution and development, and director of the Essig Museum of Entomology, writes with a passion bestowed on him by his late father, a naturalist. “....he was a used car salesman, and later, a furniture salesman, but in his heart, he was a naturalist.”
The 336-page book is captivating, transparent, and fascinating--an “I-didn't-know-that-tell-me-more!” read.
Take monarchs.
Whiteman recalls a scene from his childhood. He and his father are in a patch of milkweed. His father tears a leaf in half. As "white latex" drips from the leaf, his father tells him: "That's why they call it milkweed. Don't ever eat it. Heart poisons are in that sap.”
The toxins are terpenoids called cardiac glycosides. “One of the principal toxins in the common milkweeds that my dad and I encountered is aspecioside,” Whiteman wrote. "The monarchs obtained these heart poisons during their caterpillar stage. But the caterpillars did something even more extraordinary—they concentrated the toxin to levels even high than those found in the milkweed itself.”
“The butterflies were poisonous, my dad explained, because as caterpillars, they had eaten toxins from the milkweed leaves. The insects then stored the toxins in their bodies all the way through metamorphosis, from a zebra-striped caterpillar to a chrysalis encircled at the top by a golden diadem, to the familiar brightly colored butterfly.”
Whiteman points out that monarch butterflies "evolved to become brightly colored to warn predatory birds and other predators of the bitter and emetic cardiac glycosides within." When a bird eats a monarch, it vomits, associating "the butterfly with danger, just as Pavlov's dogs learned to associate the ring of a bell with food.”
That led Whiteman to the question “How do animals that sequester these toxins, as the monarch does, resist them?”
Whiteman researched cardiac glycosides with evolutionary ecologist Anurag Agrawal of Cornell University, who received his doctorate in population biology in 1999 from UC Davis, studying with major professor Richard "Rick" Karban, Department of Entomology and Nematology.
You'll have to read Chapter 4, "Dogbane and Digitalis," to learn what Whiteman, Agrawal and their colleagues discovered.
All 13 chapters of “Most Delicious Poison” are deliciously intriguing and inviting, from “Deadly Daisies,” “Hijacked Hormones,” “Caffeine and Nicotine” to “Devil's Breath and Silent Death” to “Opicoid Overloads” to “The Spice of Life.” And more.
His father's death in 2017 from a substance use disorder (alcohol) pushed him to write the book. "His long struggle with nature's toxins came to a head just as my collaborators and I uncovered how the monarch butterfly caterpillar resists the deadly toxins made by the milkweed host plant.”
Toxins are why the monarch can migrate thousands of miles to overwintering spots without getting eaten by predatory birds.
Nature's chemicals are not a side show, as Whiteside emphasizes. They're "the main event."
(Editor's Note: The Bohart Museum of Entomology, UC Davis, displayed Whiteman's book at its Nov. 4th open house on monarchs. Whiteman plans to deliver a presentation on the UC Davis campus sometime next spring.)
- Author: Kathy Keatley Garvey
It's one of the highest honors a scientist can receive. Members are elected to NAS in recognition of their distinguished and continuing achievements in original research.
Agrawal received his doctorate in population biology in 1999 from UC Davis, working with major professor Richard "Rick" Karban, UC Davis Department of Entomology and Nematology.
"Anurag is an inspiration as a scientist and as a person," Karban said. "I've learned a lot from him."
At Cornell, Agrawal is the James A. Perkins Professor of Environmental Studies in the College of Agriculture and Life Sciences. He researches the ecology and evolution of interactions between wild plants and their insect pests, including aspects of community interactions, chemical ecology, coevolution and the life cycle of the monarch butterfly.
Agrawal is the author of the celebrated book, Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution, published in 2017 by Princeton University Press. The book won a 2017 National Outdoor Book Award in Nature and Environment and an award of excellence in gardening and gardens from the Council of Botanical and Horticultural Libraries. It was also named one of Forbes.com's 10 best biology books of 2017. Read a review of his Monarchs and Milkweed book from the journal Ecology and read the first chapter here. (You can order the book here.)
As Agrawal said in a Cornell news release, “It's a tremendous honor and totally unexpected. I look forward to representing Cornell and also playing a part in the NAS role of advising the U.S. government on science policy.”
"A key research focus for Agrawal's Phytophagy Lab is the generally antagonistic interactions between plants and insect herbivores," according to the Cornell news release. In an attempt to understand the complexity of communitywide interactions, questions include: What ecological factors allow the coexistence of similar species? And what evolutionary factors led to the diversification of species? Agrawal's group is currently focused on three major projects: the community and evolutionary ecology of plant-herbivore relationships; factors that make non-native plants successful invaders; and novel opportunities for pest management of potatoes. Recent work on toxin sequestration in monarch butterflies was featured on the cover of the April 20 issue of Proceedings of the National Academy of Sciences."
Agrawal holds two degrees from the University of Pennsylvania, a bachelor's degree in biology and a master's degree in conservation biology. He joined the Cornell faculty in 2004 as an assistant professor of ecology and evolutionary biology, with a joint appointment in the Department of Entomology. He advanced to associate professor in 2005, and to full professor in 2010. He was named the James A. Perkins Professor of Environmental Studies in 2017.
A fellow of the American Association for the Advancement of Science (2012), and recipient of the American Society of Naturalist's E.O. Wilson Award in 2019, Agrawal won the Entomological Society of America's 2013 Founders' Memorial Award and delivered the lecture on Dame Miriam Rothschild (1908-2005) at ESA's 61st annual meeting, held in Austin, Texas.
Agrawal was at UC Davis in January of 2012 to present a seminar on "Evolutionary Ecology of Plant Defenses." His abstract: "In order to address coevolutionary interactions between milkweeds and their root feeding four-eyed beetles, I will present data on reciprocity, fitness tradeoffs, specialization and the genetics of adaptation. In addition to wonderful natural history, this work sheds light on long-standing theory about how antagonistic interactions proceed in ecological and evolutionary time."
Members are elected to NAS in recognition of their distinguished and continuing achievements in original research. Among those previously elected to NAS: Bruce Hammock, UC Davis distinguished professor of entomology who holds a joint appointment with the UC Davis Comprehensive Cancer Center. He was elected to NAS in 1999.
- Author: Kathy Keatley Garvey
We plant three species of milkweed (the host plant for the monarchs), but both the monarchs and the honey bees gravitate toward A. curassavica, a non-native. So do syrphid flies, carpenter bees, bumble bees, leafcutter bees and assorted other insects.
If you haven't heard, planting tropical milkweed is controversial. Scientific research shows that it disrupts the monarch migration patterns when it's planted outside its tropical range, and can lead to the spreading of OE, orophryocystiselektroscirrha, a protozoan parasite that infects monarch and queen butterflies. (See Exposure to Non-Native Tropical Milkweed Promotes Reproductive Development in Migratory Monarch Butterflies, published by the National Center for Biotechnology Information, U.S. National Library of Medicine, Bethesda, Md. Also see the Xerces Society for Invertebrate Conservation website on the issue.)
UC Davis alumnus and monarch expert Anurag Agrawal of Cornell University, the James A. Perkins Professor of Environmental Studies at Cornell University and the author of the celebrated book, Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and their Remarkable Story of Coevolution (2017 Princeton University), knows the controversy well.
"Tropical milkweed is an interesting and complex issue," he recently told us. "I love the plant for various reasons, but there is growing evidence that as it has become weedy (and self-seeding) in the southeastern United States and California. It is affecting monarchs, mostly by disrupting their migration. The key issue here is that when it is flowering 'out of season' this can be 'confusing' to monarchs. Having said this, we don't live in a pristine world, so my position is that we need moderation in the approach to tropical milkweed. It is certainly an easy plant to grow and monarchs can make good use of it during the caterpillar season. If you love the plant, go for it, but I would recommend cutting in back before the migratory season starts."
Agrawal received his doctorate from UC Davis. Read a review of his Monarchs and Milkweed book from the journal Ecology and read the first chapter here. You can order the book here.
Three Milkweed Species
We offer monarchs a choice of milkweed species in our Vacaville pollinator garden. In addition to the non-native A. curassavica, we plant two native species: narrowleaf milkweed, A. fascicularis, and showy milkweed, A. speciosa. In July, we collected 11 caterpillars from the narrowleaf milkweed; we rear them to adulthood and release them into the neighborhood. But in the numbers game, the tropical milkweed won. From July through today, we have collected a whopping 43 eggs or caterpillars from A. curassavica. How many from A. speciosa? Sadly, none.
As recommended, we cut back or remove the tropical milkweed before the migratory season. In the meantime, we grow it for three reasons: (1) for the monarchs (2) as a food source for other insects and (3) as an ornamental garden plant. We like the brilliant colors and the diversity of insects it attracts.
On one afternoon in late July, we photographed foraging honey bees on the spectacular blossoms. They just couldn't get enough of it.
- Author: Kathy Keatley Garvey
In research published Nov. 4 in the Proceedings of the Royal Society B, Professor Agrawal and colleague Georg Petschenka, also of Cornell, found that monarch butterflies (Danaus plexippus) have "evolved" the ability to store toxins, known as cardenolides, that are poisonous to birds. The title of their research article: "Milkweed Butterfly Resistance to Plant Toxins Is Linked to Sequestration, Not Coping with a Toxic Diet."
Lepidopterans and butterfly enthusiasts know that caterpillars digest the toxins in milkweed plants and that they retain that poison not only as caterpillars, but as chrysalids and adults.
Birds dislike the toxicity and learn to avoid the monarchs. Of course, birds still eat the caterpillars, chrysalids and adults, but not as many.
The take-home message in lay terms? "We learned that the evolutionary pressure of predation can be so strong, that it drives the way insects eat plants, and to eat more toxic plants," Agrawal told us this afternoon.
What about the oleander aphids that suck the juices out of milkweed plants and the lady beetles, aka ladybugs, that eat the aphids?
"The toxicity does impact both the aphids and lady beetles … they don't like it!" Agrawal said. "Well, it is sort of a coevolutionary argument… the aphids have specialized on the milkweeds, so that family is all they eat… but in response, the plants produce cardenolides that do bother them."
Writer Geoffrey Giller published an article, "Butterflies Weaponize Milkweed Toxins" today in The Scientist.
"Scientists," wrote Giller, "have long known that milkweed cardenolides, which in most animals disable a vital sodium-potassium pump enzyme if they are absorbed into the blood, serve to make caterpillars and butterflies dangerous meals for their predators, but whether that acquired toxicity was a side effect of an adaptation that allowed monarchs to eat milkweed or had developed separately as a defensive mechanism was unclear."
The paper is being called a landmark.
And those toxins are also "landmark" weapons. Toxic weapons.
- Author: Kathy Keatley Garvey
It will be like "old-home week" when Anurag Agrawal returns to the University of California, Davis, tomorrow (Jan. 18) to deliver a seminar on "Evolutionary Ecology of Plant Defenses."
Agrawal, who received his doctorate at UC Davis under major professor Rick Karban, UC Davis Department of Entomology, and is now a professor of ecology at Cornell University, Ithaca, N.Y., will give the presentation from 12:10 to 1 p.m., in 122 Briggs. Host is Andrew Merwin of the Michael Parrella lab.
"In order to address coevolutionary interactions between milkweeds and their root-feeding four-eyed beetles, I will present data on reciprocity, fitness tradeoffs, specialization and the genetics of adaptation," Agrawal said. "In addition to wonderful natural history, this work sheds light on long-standing theory about how antagonistic interactions proceed in ecological and evolutionary time."
Agrawal does research on plant-insect interactions, including aspects of herbivory, community ecology, phenotypic plasticity, chemical ecology and coevolution.
His research projects have included work on local biodiversity, ecology of invasive plants, the biology of Monarch butterflies, and the evolution of plant-defense strategies.
Agrawal, a native of Allentown, Penn., completed his undergraduate work in biology and his master’s degree in conservation biology at the University of Pennsylvania, where he became intrigued with plant-animal interactions.
He then headed out to California in 1994 to study with Karban, a noted expert on plant-animal interactions.
While at UC Davis, Agrawal received the 1999 Young Investigator Award, sponsored by the American Society of Naturalists. He went on to win the National Science Foundation’s 2004 Early Career Award and the Ecological Society of America’s 2006 George Mercer Award.
After receiving his doctorate from UC Davis, Agrawal accepted a postdoctoral fellowship at the University of Amsterdam before becoming an assistant professor of botany at the University of Toronto. He joined the Cornell faculty in 2004.
Among his honors: he won the sixth David Starr Jordan Prize for his innovative research involving plant-animal interactions. The international award, given approximately every three years, comes with a $20,000 prize and a commemorative medal.
In singling him out for the honor, the awards committee described Agrawal as “one of the foremost authorizes on the community and evolutionary ecology of species interactions.”
And tomorrow, Anurag Agrawal will be back on his "home turf" to talk about those interactions.