- Author: Kathy Keatley Garvey
Yes, if you use the term “personality” to refer to “intraspecific expression of behaviors that are stable over time and consistent across different situations,” says ecologist Richard “Rick” Karban, an international authority on plant communications and a distinguished professor in the UC Davis Department of Entomology and Nematology.
“Individual plants respond differently to alarm calls, just as individual animals do,” says Karban, a 40-year member of the UC Davis faculty who has studied plant communication in sagebrush (Artemisia tridentata) since 1995 on his research site, located east of the Sierra Nevada mountain range.
In a newly published paper in the international peer-reviewed journal, Oecoogia, the UC Davis professor and two colleagues found that when plants tell their neighbors—via volatile cues—that they are under attack by herbivores, the plants showed consistent individual variation in how they perceived and responded to the cues, that is, how effectively they shored up their defenses.
“The gist of the argument here is that animal behaviorists have found it useful to recognize that individual animals show behavioral tendencies that are consistent under different circumstances and repeatable over time,” Karban explained. “So, for instance, some individuals are bolder or shyer in terms of issuing or responding to alarm calls. They have termed these individual tendencies 'personalities.' We have found similar consistent individual differences among sagebrush plants.”
The paper, titled “Consistent Individual Variation in Plant Communication: Do Plants Have Personalities?,” is co-authored by Patrick Grof-Tisza of the University of Eastern Finland and Charline Couchoux of the University of Quebec. Established in 1968, Oecoogia is one of the most cited ecology journals.
“Just as animal biologists have come to consider consistent individual personalities to be an important factor in shaping animal phenotypes, behaviors, and interactions, so, too, should plant biologists include individual variation in plant communication as a significant individual attribute that influences their evolution and ecology,” they noted.
In their abstract, they explained that “When animals sense danger, some individuals will alert neighbors with alarm calls and both calling and responding vary consistently among individuals. Plants, including sagebrush, emit volatile cues when they are attacked by herbivores and neighbors perceive these cues and reduce their own damage.”
They found that 5 percent of the variance in chewing damage “was attributable to the identity of the emitter that provided the cue. This fraction of variation was statistically significant and could not be attributed to the environmental conditions of the receiver. Effective receivers were also relatively effective emitters, indicating consistency across different situations. Pairs of receivers and emitters that were effective communicators in 2018 were again relatively effective in 2019, indicating consistency over time. These results suggest that plants have repeatable individual personalities with respect to alarm calls.”
In their paper, the scientists pointed out that the goal “in discussing plant personalities is not to insinuate that plants are people or are intelligent in a similar way that we are, but to highlight that animal behavior has much to offer the development of plant biology. Recognizing that plants exhibit consistent behaviors that are repeatable in different situations and stable over time (i.e., personalities) has several important consequences.”
First, they said most plant biologists focus on treatment groups instead of individuals. “The idea that individual plants may show consistent tendencies that can be quantified, independent of other treatments, leads to a different research focus. In addition, the existence of plant personalities means that knowledge of an individual's past provides information that can predict its behavior in the future. In Bayesian jargon, the existence of personalities means that informed priors can be used to improve predictive power.”
Tradeoffs. Second, they wrote, “recognition of correlations among different plant behaviors suggests that there may be tradeoffs among important traits that are not independent of one another. For example, a negative correlation between growth of roots and shoots suggests an allocation tradeoff between above and below ground tissues while a positive correlation between growth of roots and shoots suggests that differential access to resources is more important than such an allocation tradeoff. Life-history tradeoffs of this nature are familiar to evolutionary plant biologists and this framework can be applied to other plant behaviors.”
Third, they wrote, “alarm calls that affect herbivory influence plant growth, survival, and reproduction in the few systems where they have been studied. These demographic effects have the potential to shape plant adaptations, population sizes and distributions, ability to respond to natural and human induced changes, and interactions with other species, although potential effects of variation in plant communication have been largely neglected.”
The trio pointed out that “many of these volatile chemicals dissipate rapidly so that they are present in biologically active concentrations over relatively short distances (often less than 1 m). In many instances, cues may be emitted unintentionally, and this process is probably best described as eavesdropping by the receiving plant. These same plant volatile cues have been found to serve other functions in some instances such as repelling herbivores and attracting the predators and parasites of the herbivores.”
Landmark Book. Karban is the author of the landmark book, Plant Sensing and Communication (University of Chicago Press, 2015). He is a fellow of the Ecological Society of America (ESA) and the American Association for the Advancement of Science, and the recipient of the 1990 George Mercer Award from ESA for outstanding research.
The UC Davis ecologist is featured in the Dec. 23-30, 2013 edition of The New Yorker in Michael Pollan's piece, The Intelligent Plant: Scientists Debate a New Way of Understanding Plants. Zoe Schlanger featured him in a Nov. 21, 2020 Bloomberg Quint article titled The Botanist Daring to Ask: Do Plants Have Personalities?
Karban, who holds a doctorate in biology from the University of Pennsylvania, Philadelphia, joined the UC Davis faculty in 1982.
- Author: Kathy Keatley Garvey
The honor is awarded to those scholars “whose work has been internationally recognized and acclaimed and whose teaching performance is excellent.”
The UC Davis Department of Entomology now has a total of nine distinguished professors: six current faculty--Bruce Hammock, Frank Zalom, Lynn Kimsey, James R. Carey, Jay Rosenheim, and Richard Karban--and three emeriti faculty--Harry Kaya, Howard Ferris and Thomas Scott. (In addition, emeritus professor/chair Robert E. Page Jr. is a UC Davis distinguished emeritus professor, as was the late Robbin Thorp, who died in 2019.)
Karban, whose research interests include the population regulation of animal species and the interactions between herbivores and their host plants, currently focuses his research on two main projects: volatile communication between sagebrush plants that affects resistance to herbivory and factors that control the abundance and spatial distribution of wooly bear caterpillars.
Karban has researched plant communication in sagebrush (Artemisia tridentata) on the east side of the Sierra since 1995. His groundbreaking research on plant communication among kin, published in February 2013 in the Proceedings of the Royal Society B: Biological Sciences, drew international attention. In that study, Karban and his co-researchers found that 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.”
On his website, he explains his research on volatile communication: “When sagebrush is experimentally clipped, it releases volatile cues that undamaged branches on the same plant, on different sagebrush plants, and on some other plant species respond to. These volatile cues cause many changes in neighboring plants and some of these changes make the undamaged neighbors better defended against their herbivores. We currently know little about the nature of these cues.
“Blocking air contact between branches makes responses undetectable, indicating the involvement of airborne cues. Methyl jasmonate has the ability to serve as the signal although it remains unclear if it acts in this capacity in nature. I would like to understand the costs and benefits of releasing volatiles cues and of responding to them. I am examining the multiple consequences of emitting cues. For example, cues affect neighboring plants, nearby herbivores, as well as predators and parasites of those herbivores. I am currently examining the long-term fitness consequences for sagebrush of responding to volatile cues.”
On his research on the abundance and distribution of caterpillars, Karban writes: “Many workers define ecology as the science that explains the abundance and distribution of species. Despite a century of work on these questions, our field has only a rudimentary grasp on the factors that are important. I have been censusing populations of wooly bear caterpillars at Bodega Bay for 30 years and have relatively little understanding of the factors that produce patterns in abundance and distribution. The ‘usual suspects' all have relatively little explanatory power: weather, food limitation, and parasitoids all fail to provide much insight. Indeed, caterpillars often recover from the attacks of their tachinid parasitoids and alter their diets when parasitized to increase their chances of surviving. Including a more complete food web in our analysis does not appear to provide more resolution although ants may be unappreciated as predators and food quality may also be important. I am collaborating with Perry de Valpine to attempt to develop new analytical techniques that will account for more of the variance in abundance data. I am collaborating as well with Marcel Holyoak to examine spatial patterns of abundance.”
Karban is the author of landmark book, Plant Sensing and Communication. He is a fellow of the Ecological Society of America (ESA) and the American Association for the Advancement of Science, and the recipient of the 1990 George Mercer Award from ESA for outstanding research.
The UC Davis ecologist is featured in the Dec. 23-30, 2013 edition of The New Yorker in Michael Pollan's piece, The Intelligent Plant: Scientists Debate a New Way of Understanding Plants. Zoe Schlanger featured him in a Nov. 21, 2020 Bloomberg Quint article titled The Botanist Daring to Ask: Do Plants Have Personalities?
Karban received his bachelor's degree in environmental studies from Haverford (Penn.) College in 1977 and his doctorate in biology from the University of Pennsylvania, Philadelphia, in 1982. He served as a lecturer at Haverford College for six months before joining the UC Davis faculty in May 1982 as an assistant professor. He advanced to associate professor in 1988 and to full professor in 1994.
- Author: Kathy Keatley Garvey
A recent article in Science headlined "Once Considered Outlandish, the Idea that Plants Help their Relatives Is Taking Root," and dealing with how plants communicate, is drawing widespread attention.
Wrote Elizabeth Pennisi: "For people, and many other animals, family matters. Consider how many jobs go to relatives. Or how an ant will ruthlessly attack intruder ants but rescue injured, closely related nestmates. There are good evolutionary reasons to aid relatives, after all. Now, it seems, family feelings may stir in plants as well."
"A Canadian biologist planted the seed of the idea more than a decade ago, but many plant biologists regarded it as heretical—plants lack the nervous systems that enable animals to recognize kin, so how can they know their relatives? But with a series of recent findings, the notion that plants really do care for their most genetically close peers—in a quiet, plant-y way—is taking root. Some species constrain how far their roots spread, others change how many flowers they produce, and a few tilt or shift their leaves to minimize shading of neighboring plants, favoring related individuals."
Pennisi quoted ecologist Richard "Rick" Karban, professor in the UC Davis Department of Entomology and Nematology, for her piece. An international authority on plant communication, he authored the 240-page book, Plant Sensing and Communication (University of Chicago Press), considered a landmark in its field.
An excerpt from Science: "Sagebrush bushes (Artemisia tridentata) have provided some strong clues, however. When injured by herbivores, these plants release volatile chemicals that stimulate neighboring sagebrush to make chemicals toxic to their shared enemies. Ecologist Richard Karban at the University of California, Davis, wondered whether kin were preferentially warned. His group had already found that sagebrush plants roughly fall into two "chemotypes," which mainly emit either camphor or another organic compound called thujone when their leaves are damaged. The team showed that the chemotypes are heritable, making them a potential kin recognition signal. In 2014, the researchers reported that when volatiles from a plant of one chemotype were applied to the same type of plant, those plants mounted stronger antiherbivore defenses and had much less insect damage than when the volatiles were applied to a plant of the other chemotype—a hint of a kin effect."
She concluded with a quote from Karban: "We are learning that plants are capable of so much more sophisticated behavior than we had thought. It's really cool stuff."
Update?
"We aren't actually doing more work that addresses the issue of kin recognition," Karban told us. "We have found that sagebrush plants communicate more effectively with kin than strangers and more effectively with other individuals that belong to the same 'chemotype' as they do. Chemotypes are similar to blood types - they represent chemical variation among individuals in the population. As with blood types, it is puzzling why this variation exists. The cues that sagebrush use to communicate are potentially extremely complex; we can identify on the order of 100 volatile compounds that are emitted by damaged foliage. This gives an enormous number of possible 'words' that could provide information in the 'language' that the plants may be using. Since the chemotypes differ in only a few compounds, we are hoping that focusing on chemotypic variation will provide some clues that help us begin to decipher the language of the plants.
Karban has researched plant communication in Artemisia tridentataon the east side of the Sierra since 1995. His groundbreaking research on plant communication among kin, published in February 2013 in the Proceedings of the Royal Society B: Biological Sciences, drew international attention. In that study, Karban and his co-researchers found that 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.”
“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,” Karban wrote.
The gist of it: if you're a sagebrush and a predator (such as a grasshopper) is eating your nearby kin, another sagebrush, 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. Yes, plants can communicate.
We remember asking Karban several years go "the 10 things to know about plant sensing and communication." According to Karban:
- Plants sense their environments and respond.
- Although they lack central nervous systems, they process information and appear to "behave intelligently."
- They sense the position of competitors and "forage" for light.
- They sense the availability of water and nutrients in the soil and "forage" for these resources.
- Their decisions are influenced by past experiences, akin to memory.
- They respond to reliable cues that predict future events, allowing them to "anticipate."
- Plants respond differently to cues that they themselves produce, allowing them to distinguish self from non-self.
- They respond differently to close relatives and strangers.
- Plants that are prevented from sensing or responding experience reduced fitness.
- By understanding the "language" of plant responses, we can grow healthier and more productive plants.
The most basic form of communication? When a plant is being shaded, it senses the diminished light quality caused by a competitor and responds by moving away, Karban says.
Karban's work on plant communication is featured in a 2016 interactive lesson plan, TED-Ed Original Lessons where "words and ideas of educators are brought to life by professional animators.” Plants can eavesdrop, sense danger in the environment, and can distinguish friend from foe, he says.
- Author: Kathy Keatley Garvey
Yes, they can.
And now UC Davis ecologist Richard “Rick” Karban's research is “talking” in TED-Ed Original Lessons and drawing international attention from thousands of teachers, their students and other Internet viewers.
Karban's work on plant communication is featured in an interactive lesson plan where "words and ideas of educators are brought to life by professional animators.” Teachers can customize the lesson plan to engage their students.
Plants can eavesdrop, sense danger in the environment, and can distinguish friend from foe, says Karban, a professor in the UC Davis Department of Entomology and Nematology, who recently published a 250-page comprehensive book, Plant Sensing and Communication (University of Chicago Press), hailed as a landmark in its field.
A plant under a predatory attack will emit volatile chemical cues, enabling its neighboring plants to adjust their defenses to better protect themselves.
Nearly 130,000 have accessed the lessons, with nearly 2000 questions answered. In the TED-ED lessons, teachers can interact with their students, quizzing them on:
- What are some characteristics of the language of plants?
- Why do plants communicate? What advantages might they get from communicating that increase their chances of survival and reproduction?
- In what ways are communication systems between plants similar to communication systems between animals? In what ways are they different?
The creators of the plant communication lesson are Karban, educator; Yukai Du, director; Angus MacRae, composer; Eleanor Nelson, script editor; and Jiaqi Wang, animator.
Karban has researched plant communication in sagebrush (Artemisia tridentata) on the east side of the Sierra since 1995. His groundbreaking research on plant communication among kin, published in February 2013 in the Proceedings of the Royal Society B: Biological Sciences, drew international attention. In that study, Karban and his co-researchers found that 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.”
“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.
In other words, if you're a sagebrush and your nearby kin is being eaten by a grasshopper, deer, jackrabbit, caterpillar or other predator, communication is more effective if you're closely related. Through volatile cues, your kin will inform you of the danger so you can adjust your defenses.
Karban likened this kind of plant communication to eavesdropping.” Plants “hear” the volatile cues of their neighbors as predators damage them.
The most basic form of communication? When a plant is being shaded, it senses the diminished light quality caused by a competitor and responds by moving away, Karban says.
What are 10 things to know about plant sensing and communication? According to Karban:
- Plants sense their environments and respond.
- Although they lack central nervous systems, they process information and appear to "behave intelligently."
- They sense the position of competitors and "forage" for light.
- They sense the availability of water and nutrients in the soil and "forage" for these resources.
- Their decisions are influenced by past experiences, akin to memory.
- The respond to reliable cues that predict future events, allowing them to "anticipate."
- Plants respond differently to cues that they themselves produce, allowing them to distinguish self from non-self.
- They respond differently to close relatives and strangers.
- Plants that are prevented from sensing or responding experience reduced fitness.
- By understanding the "language" of plant responses, we can grow healthier and more productive plants.
The most basic form of communication? When a plant is being shaded, it senses the diminished light quality caused by a competitor and responds by moving away, Karban says.
Karban is a fellow of the American Association for the Advancement of Science (AAAS) and has published more than 100 journal articles and now, three books.
Karban is featured in the Dec. 23-30, 2013 edition of The New Yorker in Michael Pollan's piece, “The Intelligent Plant: Scientists Debate a New Way of Understanding Plants."
Related Link:
Rick Karban: Kin Recognition Affects Plant Communication and Defense
- Author: Kathy Keatley Garvey
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?