Nectar-living microbes release scents or volatile compounds, too, and can influence a pollinator's foraging preference, according to newly published research led by UC Davis community ecologist Rachel Vannette.
The groundbreaking research, published in the current edition of New Phytologist journal, shows that nectar-inhabiting species of bacteria and fungi “can influence pollinator preference through differential volatile production,” said Vannette, an assistant professor in the UC Davis Department of Entomology and Nematology.
“This extends our understanding of how microbial species can differentially influence plant phenotype and species interactions through a previously overlooked mechanism,” Vannette said. “It's a novel mechanism by which the presence and species composition of the microbiome can influence pollination.”
“Broadly, our results imply that the microbiome can contribute to plant volatile phenotype,” she said. “This has implications for many plant-insect interactions.”
Their paper, titled “Nectar-inhabiting Microorganisms Influence Nectar Volatile Composition and Attractiveness to a Generalist Pollinator,” may explain in part the previous documented extreme variation floral volatiles that Robert Junker of University of Salzburg, Austria, and his team found; New Phytologist published their work in March 2017.
Although microbes commonly inhabit floral nectar, microbial species differ in volatile profiles, they found. “Honey bees detected most of the microbial volatiles or scents that we tested,” Vannette said, “and they distinguished the solutions of yeasts or bacteria based on volatiles only.” This suggests that pollinators could choose among flowers based on the microbes that inhabit those flowers.
The yeast Metschnikowia reukaufii produced the most distinctive compounds (some shared with the fruity flavors in wine) and was the most attractive of all microbes compared. This yeast is commonly found in flower nectar and is thought to hitch a ride on pollinators to travel from one flower to the next. Its scent production may help it attract pollinators, which then help the yeast disperse among flowers.
The Harry H. Laidlaw Jr. Honey Bee Research Facility, UC Davis, provided the honey bees. More than 20 species of flowers--mostly natives--were used in the survey, including canyon delphinium or canyon larkspur (Delphinium nudicaule), sticky monkey flower (Mimulus aurantiacus), salvia (Lepechinia calycina) and purple Chinese houses (Collinsia heterophylla). The samplings were done in the spring and early summer, when the natives are at their peak.
Co-authors of the paper are Caitlin Rering, postdoctoral fellow at USDA-ARS, Gainesville, Fla.; John Beck researcher at USDA-ARS; Griffin Hall, junior specialist in the Vannette lab; and Mitch McCartney in UC Davis Department of Mechanical and Aerospace Engineering.
The USDA and USDA-ARS funded the research.
All will take place on Wednesdays from 4:10 to 5 p.m. in 122 Briggs Hall, Kleiber Hall Drive.
Coordinator Rachel Vannette, assistant professor of entomology, has announced the following:
Sept. 27: “Bug Smell: Evolution of Communication” by Zain Syed of the University of Notre Dame, formerly of the UC Davis Department of Entomology and Nematology
Oct. 4: “Genomic Signatures of Social Evolution in Social Insects” by Tim Linksvayer, University of Pennsylvania
Oct. 11: “Multitrophic Mediation of Plant Perception of Herbivores” by Gary Felton, Pennsylvania State University, who received his doctorate in entomology from UC Davis
Oct. 18: Exit seminar by Leslie Saul-Gershenz, doctoral candidate, UC Davis Department of Entomology and Nematology
Oct. 25: "Ecoinformatics and the Curious Case of Katydids in California Citrus" by Bodil Cass, UC Davis
Nov. 1: “Mating Distruption of Glassy-Winged Sharpshooter by Playback of Natural Vibrational Signals in Vineyard Trellis” by Rodrigo Krugner of the U.S,. Department of Agriculture/Agricultural Research Service (USDA-ARS)
Nov. 8: Exit seminar by doctoral candidate/ecologist Ash Zemenick, UC Davis Department of Entomology and Nematology
Nov. 15: “Revelations from Phasmatodea Digestive Track Transcriptomics” by Matan Shelomi, National Taiwan University, who received his doctorate in entomology from the UC Davis Department of Entomology and Nematology
Nov. 22: Thanksgiving week; no seminar
Nov. 29; “Ant Social Parasites Repeatedly Evolved Reproduction Isolation from Their Hosts in Sympatry” by Christian Rabeling, Arizona State University
Dec. 6: “Root Knot Nematode and Associated Pathogen Resistance” by Phil Roberts, University of Riverside
Cookies will be provided prior to the seminar. For more information on the seminars, contact Vannette at firstname.lastname@example.org or graduate program coordinator Jessica Padilla at email@example.com.
Download flyer below:
The non-profit educational organization, geared for small-scale beekeepers in the western United States, is headed by president Eric Mussen, Extension apiculturist emeritus, of UC Davis.
WAS has already booked Kim Flottum of Medina, Ohio, editor of Bee Culture; Les Crowder of Austin, Texas, author of Top-Bar Beekeeping; Gene Brandi of Los Banos, president of the American Beekeeping Federation; Larry Connor of Kalamazoo, Mich., author and beekeeper; Rod Scarlett, executive director, Canadian Honey Council, and Slava Strogolov, chief executive officer of Strong Microbials Inc., Milwaukee.
- Extension apiculturist Elina Lastro Niño will speak on “Impact of Varroa on Honey Bee Reproductive Castes): Where Will the Research Lead Us?” at at 8:30 a.m. The three reproductive castes are the queen and worker bee (female), and drone (male).
- Associate professor Brian Johnson will speak on “Geographical Distribution of Africanized Bees in California” at 9 a.m., He will show “the results of a genotyping study of bees caught from across California showing the current distribution of Africanized Honey Bees in our state."
- Distinguished emeritus professor Robbin Thorp, a native pollinator specialist, will discuss “Life Cycles of Commonly Encountered Native Bee Genera" at 10:30 a.m. He is the co-author of Bumble Bees of North America: an Identification Guide and California Bees and Blooms: A Guide for Gardeners and Naturalists.
- Professor Neal Williams, a pollination ecologist, will discuss “Known and Potential of Native Bees in Crop Pollination” at 11 a.m.
Casey also will lead a tour of the haven at 9:30 a.m. on Wednesday, Sept. 6. “The Haven is a unique outdoor museum designed to educate visitors about bees and the plants that support them," she says. "Tour participants will see some of our 85 bee and 200 plant species, learn about our outreach and research programs, and gain ideas for their own bee gardens." Other tours are to Mann Lake facility and Z Specialty Foods, both in Woodland.
On Friday, Sept. 8, Extension apiculturist emeritus Eric Mussen will moderate a panel on “Pesticide Toxicity Testing with Adult and Immature Honey Bees.” The panel will convene at 9:15 a.m. At 1:30 on Friday, assistant professor Rachel Vannette of UC Davis will discuss “Variation in Nectar Quality Influence Pollinator Foraging." She studies floral nectar chemistry and microbiology and examines how these characteristics of flowers mediate interactions between plants and pollinators
Other UC Davis highlights:
Honey Tasting: Amina Harris, director of the Honey and Pollination Center at the Robert Mondavi Institute of Wine and Food Science, UC Davis, will lead a moderated honey tasting at 11 a.m. on Wednesday, Sept. 6. The event is titled “Taste the Honey Flavors of the West: How Understanding the Nuances of your Honey Can Help You Market your Perfect Sweet.” Said Harris: "Basically I plan to discuss the diversity and life styles of non-Apis bees to show how different most are from honey bees."
Memories: The founders of WAS will discuss "how it all began" from 8:45 to 9:30 a.m. on Wednesday, Sept. 6. The organization, founded at UC Davis, was the brainchild of Norm Gary, then professor of apiculture (now emeritus), who served as the first WAS president. Assisting him in founding the organization were Eric Mussen, then an Extension apiculturist who was elected the first WAS vice president; and postdoctoral fellow Becky Westerdahl, now a nematologist in the department, who held the office of secretary-treasurer.
More information on the conference is available from the WAS website or contact Eric Mussen, serving his sixth term as president, at firstname.lastname@example.org. Registration is underway at http://www.westernapiculturalsociety.org/2017-conference-registration/
In newly published research in Ecology Letters, "Dispersal Enchances Beta Diversity in Nectar Microbes," Vannette and colleague Tadashi Fukami of Stanford University's Department of Biology, examined microbial communities inhabiting the nectar of the sticky monkeyflower, Mimulus auranticus, at the Jasper Ridge Biological Preserve in California's Santa Cruz Mountains.
The flower, in the family Phrymacease, is a native shrub common in chaparral and coastal scrub habitats of California and Oregon. It is primarily pollinated by Anna's hummingbird. Other common pollinators include bumble bees, carpenter bees, and thrips.
Dispersal is considered a key driver of beta diversity, which is “the variation in species composition among local communities,” Vannette said.
They are the first to publish work showing that increased dispersal can increase biodiversity.
In their experiment, they reduced natural rates of dispersal by eliminating multiple modes of microbial dispersal. “Specifically we focused in nectar-inhabiting bacteria and yeasts that are dispersed among flowers by wind, insects and birds,” they said. “We imposed dispersal limitation on individual flowers and quantified microbial abundance, species composition and microbial effects on nectar chemistry.”
This work has direct implications for conservation of many organisms in addition to bacteria and yeast, suggesting that preserving routes of dispersal among habitat patches may be important in the maintenance of biodiversity. In contrast to previous work showing that dispersal can homogenize communities or make them more similar, the published work demonstrates that dispersal can in some cases generate communities that are more different from each other. The authors hypothesize that this could be driven by priority effects, where early arriving species change the species that can establish within that habitat.
Why focus on nectar-inhabiting microbes? Previous work by Vannette and others shows that microbial activity in nectar can alter nectar chemistry and influence plant-pollinator interactions by altering nectar chemistry. In the Ecology Letters study, microbes were also found to change nectar chemistry, explaining ~50% of the variation in sugar composition in the field. This suggests that nectar-inhabiting bacteria and yeast can influence the nectar rewards available to pollinators in a natural setting.
More broadly, “Studying the role of microbes in the environment addresses one of the biggest mysteries in science,” Vannette says. In her current work, she and her lab are investigating how microbial communities form, change, and function in their interactions with insects and plants. They are also researching how microorganisms affect plant defense against herbivores and plant attraction to pollinators.
Vannette, a former postdoctoral fellow at Stanford, joined the UC Davis Department of Entomology and Nematology faculty as an assistant professor in 2015.
Vannette's research was funded by the Gordon and Betty Moore Foundation through the Life Sciences Research Fellowship. Stanford also funded the research through grants from the National Science Foundation, the Terman Fellowship, and the Department of Biology at Stanford University.
- Evolution of floral signals and flower morphology
- Pollinator-drive speciation
- Evolution of floral mimicry
For upcoming seminars, download this PDF