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It Pays to Be a Relative
Plants communicate. They do.
Ecologist Richard Karban, a professor in the UC Davis Department of Entomology, points out that one of the simplest forms of communication involves shade.
When a plant is shaded, it grows away from the plant or other object that's shading it.
Today he published research in the Proceedings of the Royal Society B: Biological Sciences that is truly amazing readers. It involves kinship, communication and defenses.
Basically, if you’re a sagebrush and your nearby kin is being eaten by a grasshopper, deer, jackrabbit, caterpillar or other predator, it’s good to be closely related. Through volatile (chemical) cues, your kin will inform you of the danger so you can adjust your defenses.
If you’re not closely related, communication won’t be as effective.
Kin have distinct advantages when it comes to plant communication, just as “the ability of many animals to recognize kin has allowed them to evolve diverse cooperative behaviors," Karban says. For example, fire ants can recognize kin. “Ants will destroy queens that are not relatives but protect those who are."
That ability is less well studied for plants--until now.
“When sagebrush plants are damaged by their herbivores, they emit volatiles that cause their neighbors to adjust their defenses,” Karban said. “These adjustments reduce rates of damage and increase growth and survival of the neighbors.”
“When sagebrush plants are damaged by their herbivores, they emit volatiles that cause their neighbors to adjust their defenses,” Karban said. “These adjustments reduce rates of damage and increase growth and survival of the neighbors.”
“Why would plants emit these volatiles which become public information?” he asked. “Our results indicate that the volatile cues are not completely public, that related individuals responded more effectively to the volatiles than did strangers. This bias makes it less likely that emitters will aid strangers and more likely that receivers will respond to relatives.”
The research, “Kin Recognition Affects Plant Communication and Defense,” is co-authored by two scientists from Japan and two from UC Davis: Kaori Shiojiri of the Hakubi Center for Advanced Research, Kyoto University, and Satomi Ishizaki of the Graduate School of Science and Technology, Niigata University; and William Wetzel of the UC Davis Center for Population Biology, and Richard Evans of the UC Davis Department of Plant Science.
To simulate predator damage, the researchers “wounded” the plants by clipping them and then studied the responses to the volatile cues. They found that the plants that received cues from experimentally clipped close relatives experienced less leaf damage over the growing season that those that received cues from clipped neighbors that were more distantly related.
“More effective defense adds to a growing list of favorable consequences of kin recognition for plants,” they wrote.
The researchers performed their field work on sagebrush (Artemisia tridentata) at Taylor Meadow, UC Sagehen Creek Field Station, near Truckee. They conducted four field experiments over three years “that compared the proportion of leaves that were damaged by herbivores over the growing season when plants were provided with volatile cues clipped from a close relative versus cues from a distant relative,” the scientists wrote.
For closely related kin, they snipped stem cuttings (clones), potted them, and then returned the pots to the field. They determined relatedness “by using microsatellites that varied among individual sagebrush clones.”
The result: “Plants responded more effectively to volatile cues from close relatives than from distant relatives in all four experiments and communication reduced levels of leaf damage experienced over the three growing seasons,” they wrote. “This result was unlikely to be caused by volatiles repelling or poisoning insect herbivores.”
Karban, who has studied plant communication among the sagebrush at the site since 1999, likened the plant communication to neighbors “eavesdropping.” They “hear” the volatile cues of their neighbors as predators damage them.
Eavesdropping. Kinship. Plant communication. Plant defenses.
Fascinating stuff.
Who knew?
Grasshopper feeding on sagebrush. (Photo courtesy of Rick Karban)
Rick Karban collecting volatile (chemical) cues.
Feeding Frenzy on Bodega Head
If you're planning to hike the hills around Bodega Head in Sonoma County, watch out for the bears.
The woolly bear caterpillars, that is.
Last Sunday, with the temperature hovering around 70 degrees, the woolly bears were everywhere. They were munching on the gray-green leaves of Lupinus arboreus (yellow bush lupine), not yet blooming. We also spotted them on yellow mustard and wild radish, both members of the Brassicaceae family and both abloom.
If you look closely at these little caterpillars, they seem to be having a bad hair day. They look as if they just encountered a jolt of static electricity.
They're also known as the larvae of Ranchman's Tiger Moth (Platyprepia virginalis). Once they become moths, they do not resemble woolly bears any more.
Rick Karban, professor of entomology at UC Davis, has published a number of research papers on these herbivores.
"Platyprepia virginalis caterpillars are dietary generalists and feed on multiple host species within a single day," he wrote recently in Ecological Entomology. "We conducted field experiments to evaluate their performance on diets consisting of only their primary food, Lupinus arboreus, or diets consisting of L. arboreus plus other acceptable host species."
"We found that relative growth rates and rates of survival were higher when they fed on mixed diets compared to lupine only."
That feeding behavior we saw, too. A lupine lunch, with a touch of mustard and radish.
Close-up of woolly bear caterpillar on yellow lupine on Bodega Head, Sonoma County. (Photo by Kathy Keatley Garvey)
Woolly bear caterpillar on wild radish on Bodega Head, Sonoma County. (Photo by Kathy Keatley Garvey)
Evolutionary Ecology of Plant Defenses
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.
Anurag Agrawal, professor of evolution and ecology at Cornell, returns to the UC Davis campus Jan. 18 to give a seminar.
A Woolly Bear of a Caterpillar
If you enjoy climbing the cliffs of Bodega Head on the Sonoma coast, keep your eyes out for bears--woolly bear caterpillars, that is.
The so-called "woolly bear caterpillar" is reddish, black and woolly and has a voracious appetite much like that of Joey Chestnut. It is the Ranchman's Tiger Moth caterpillar, Platyprepia virginalis.
Richard "Rick" Karban, professor of entomology at the University of California, Davis, studies this critter. "It has a taste for most alkaloid containing plants, like fiddleneck, although it doesn't appear to sequester the alkaloids," he told us. "The alkaloids may help caterpillars survive their parasitoids, however."
We saw about five of the woolly bear caterpillars on a public trail near the Bodega Marine Reserve above the Bodega Marine Laboratory on April 17.
The reserve, which surrounds the Bodega Marine Laboratory, is a unit of the University of California Natural Reserve System and is administered by UC Davis.
Several woolly bear caterpillars were munching on fiddleneck. Another rolled around near a patch of California poppies and we couldn't tell what its menu included. It looked good, though!
You can read Karban's research on "Diet Mixing Enhances the Performance of a Generalist Caterpillar, Platyprepia virginalis," published last February in the Ecological Entomology journal.
A woolly bear caterpillar munching on foliage at the Bodega Head. (Photo by Kathy Keatley Garvey)
A woolly bear caterpillar munching on fiddleneck. (Photo by Kathy Keatley Garvey)
Prized Award
Evolutionary ecologist Anurag Agrawal (right), who received his doctorate in population biology from the University of California, Davis in 1999 under major professor Richard “Rick” Karban, has just received the sixth David Starr Jordan Prize for his innovative research inolving plant-animal interactions.
The international award, given approximately every three years, comes with a $20,000 prize and a commemorative medal.
Agrawal, now an associate professor in the Department of Ecology and Evolutionary Biology, Cornell University, also serves as the associate director for the Cornell Center for a Sustainable Future and director of the Cornell Chemical Ecology Group.
Does the name "David Starr Jordan" ring a bell? It should. He was a leading American biologist (1851-1931) who was educated at Cornell; taught zoology at Indiana; and served as president of both Indiana and Stanford universities.
The three universities established the joint endowment in 1986 and have awarded the prize since 1987. “The intent of the David Starr Jordan Prize is to recognize scientists who are making research contributions likely to redirect the principal foci of their fields,” the awards committee said.
The coveted award is given to a young scientist, age 40 or under, who is making novel innovative contributions in one of Jordan’s fields of interest: evolution, ecology, population and organismal biology.
The awards committee, comprised of Cornell, Indiana and Stanford scientists, described Agrawal as “one of the foremost authorities on the community and evolutionary ecology of species interactions.”
“Dr. Agrawal has made highly influential contributions, including empirical and conceptual advances in our understanding of plant defense against herbivory, impacts of genetic diversity on community processes, co evolutionary interactions between monarch butterflies and milkweeds and deciphering the success of invasive plants,” the committee announced.
As the recipient of the David Starr Jordan Prize, he will lecture at the sponsoring institutions, beginning Feb. 18 at Cornell.
Born in 1972 in Allentown, Penn., Agrawal 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. Karban, now a newly elected Fellow of the American Association for the Advancement of Science, teaches field ecology and community ecology.
“It was an amazing time being a graduate student at UC Davis and working with Rick Karban… a great foundation and nothing but great memories!” Agrawal said.
Monarch Butterfly
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