- Author: Kathy Keatley Garvey
Yes, according to UC Davis community ecologist and doctoral candidate Danielle Rutkowski and her colleagues in their newly published research in the Royal Entomological Society's Journal of Ecological Entomology.
The research, “Bee-Associated Fungi Mediate Effects of Fungicides on Bumble Bees,” provides direct evidence that fungi can benefit both survival and reproduction in two species of bumble bees, Bombus vosnesenskii, and B. impatiens. The research also suggests that yeast, commonly found in the gut of bumble bees, may be more important than originally thought.
“Bumble bees are important pollinators that face threats from multiple sources, including agrochemical application,” said Rutkowsi, the lead researcher-author. “Declining bumble bee populations have been linked to fungicide application, which could directly affect the fungi often found in the stored food and gastrointestinal (GI) tract of healthy bumble bees.”
“I tested if fungicides commonly applied in orchard systems affected yeasts and the health of their bee hosts, and if feeding those bees their fungi after fungicide exposure could rescue them,” said Rutkowski, who studies with major professors Rachel Vannette and Richard Karban, community ecologists in the Department of Entomology and Nematology.
“Bombus vosnesenskii (commonly known as the yellow-faced bumble bee), is native to California and we reared colonies of it from wild-caught queens,” Rutkowski said. “In this species, we observed strong negative effects of fungicide and the ability of bee-associated fungi to rescue bees from these negative effects. The other species, Bombus impatiens, is native to the eastern United States, but is commonly produced and sold commercially for pollination. In this species, we did not find any negative impacts of fungicide, but the addition of yeasts was very beneficial for bee survival and offspring production.”
“Although most previous work on bee microbiomes has focused on bacteria and their role in bee health, Danielle's work suggests that yeasts --which are commonly found in association with bumble bees--may be more important than previously thought,” Vannette said. “This has been hinted at in the literature but rarely tested directly.”
Rutkowski examined the interactive effects of the fungicide propiconazole and fungal supplementation on the survival, reproduction and microbiome composition of microcolonies (queenless colonies) using the two species.
Both B. vosnesenskii and B. impatiens benefitted from fungal addition but in different ways. fungicide exposure decreased survival in B. vosnesenskii, while fungal supplementation mitigated fungicide effects. For B. impatiens, fungicide application had no effect, but fungal supplementation improved survival and offspring production.
“Because the effect of fungicides on yeasts and bees takes a few weeks to observe, it is not detected in short term LD50 trials,” Vannette said, “and therefore could be an unrecognized threat to bumble bees and their symbionts.”
Other co-authors of the paper are entomologist Eliza Litsey and environmental scientist Isabelle Maalouf.
More research is planned to determine the mechanism by which yeasts can affect bee health, and which fungicides affect bee-associated yeasts.
“I'm currently working on a project to determine the mechanisms behind the positive effects of yeast addition that we observed,” Rutkowski said. “In some bees and other insects, fungi can produce nutritionally important compounds for their host, and I'm currently trying to determine if this is the case for bumble bees as well.”
“Additionally, I'm planning on following up some of the interesting results on differences between bumble bee species by determining how associated microbial communities differ between wild and commercially-reared bumble bees,” Rutkowski said. “In this current paper, we found that the fungal communities associated with the commercially-sourced bees were less diverse and less abundant, and I'm hoping to determine if that's a common pattern.”
Rutkowski, who joined the UC Davis doctoral program in 2018, won the President's Prize (first-place) in her category for her graduate student research presentations at the 2017 and 2021 Entomological Society of America meetings. A 2018 graduate of Cornell University, summa cum laude, she holds a bachelor of science degree in entomology and biological sciences, with a concentration in ecology and evolution.
Rutkowski's research drew support from her three-year USDA National Institute of Food and Agriculture grant.
- Author: Kathy Keatley Garvey
Squirm, maggots, squirm!
If you look behind the scenes of the entomological activities at the 108th annual UC Davis Picnic Day on Saturday, April 23 at Briggs Hall, you'll see a Department of Entomology and Nematology doctoral candidate coordinating everything from Roach Races to Maggot Art.
“I'm really excited to get our events up and running again after two years," said Danielle Rutkowski, the UC Davis Graduate Student Association (EGSA) coordinator of the department's Picnic Day activities at Briggs Hall (with forensic entomologist and faculty member Robert Kimsey).
COVID-19 pandemic cancelled the in-person UC Davis Picnic Day in both 2020 and 2021, but not 2022, nor the renewed enthusiasm.
“Coordinating events has been challenging, mostly because I've only been to one in-person Picnic Day myself!" said Rutkowski, who enrolled in the doctoral program in 2018, and is advised by associate professor Rachel Vannette and UC Davis distinguished professor Richard Karban.
"But it's been fun to work with other graduate students and the entomology club to get our exhibits from previous years back together. This is the first Picnic Day for many students in the department, so I want to make sure it's a fun experience for volunteers as well as visitors.”
Entomological activities at Briggs Hall will include Bug Doctor and Doctor Death booths; displays featuring honey bees, ants, mosquitoes, integrated pest management, forest entomology, medical entomology and agricultural entomology; and EGSA's insect-themed t-shirt sales, as well as the crowd-pleasing Roach Races and Maggot Art. And more. (See schedule at Briggs and Bohart Museum of Entomology.)
“The Roach Races are a definite favorite of the public; they're really high energy and a lot of fun," Rutkowski said. "And the (American) roaches are from a colony that the entomology club cares for, so they can return home after a hard day of racing. Maggot Art is another popular event among visitors, and we order the maggots from a bait supplier.”
Rutkowski says there are plenty of events “that I haven't seen before, and I'm looking forward to being a part of them this year. We'll have a lot of displays set up in Briggs 122, which I'm excited to see. We'll be bringing back some previous displays on forest entomology and medical entomology, as well as some new displays on agricultural entomology and caterpillar biology.”
Her research is funded by a three-year USDA National Institute of Food and Agriculture (NIFA) pre-doctoral fellowship of $180,000; it provides tuition stipends and research funding to study the impacts and mechanisms of fungicide and bee-associated fungi on bumble bee health. Her other grants or scholarships include a 2020 Academic Senate grant of $25,000 to research the effects of fungicide on the health and microbiome composition of bumble bees; three George H. Vansell Scholarships (2019, 2020 and 2021 totaling $8950) to study the effects of fungicide on the health and microbiome composition of bumble bees; and a 2018-2020 UC Davis Eugene Cota-Robles Fellowship of $95,200.
Danielle holds a bachelor of science degree from Cornell University in entomology and biological sciences, with a concentration in ecology and evolutionary biology. She graduated in May 2018 summa cum laude with distinction in research.
At Cornell, Rutkowski worked with Professor Richard Lindroth on multiple projects investigating how genotype and environmental conditions interact to affect the growth, defense, and insect community of aspen trees. She did independent research with Professor Jennifer Thaler, carrying out an independent honor's thesis research project on ecological interactions between insect herbivores, plants, and arbuscular mycorrhizal fungi. Rutkowski also worked with Thaler on numerous other projects, studying interactions between potato plants, Colorado potato beetles, and their predators, as well as projects studying the interactions between arbuscular mycorrhizal fungi, tomato plants, and insect herbivores.
Active in the Entomological Society of America (ESA), Rutkowski presented her research at the annual meetings in 2017, 2018 and 2021, and received the President's Prize (first place) in both 2017 and 2021. Rutkowski has also served as a member of the UC Davis graduate student group, Equity in Science, Technology, Engineering, Math, and Entrepreneurship (ESTEME), planning activities and lessons for middle school students in the Davis area.
But for now, Danielle Rutkowski is juggling (1) her research on bumble bees (2) her dedication to her academic studies and (3) her mentoring and student teaching with (4) her commitment to public service: coordinating the highly popular Roach Races, Maggot Art and other entomological activities at the UC Davis Picnic Day's campuswide open house.
- Author: Kathy Keatley Garvey
Hammer will speak at 4:10 p.m. in 122 Briggs Hall. The Zoom link:
https://ucdavis.zoom.us/j/99515291076.
Community ecologist Rachel Vannette, associate professor, UC Davis Department of Entomology and Nematology, is hosting the seminar.
"How do insects and microbes form symbioses, and why do these partnerships often break down?" Hammer asks in his abstract. "We are addressing these questions with the gut microbiomes of social corbiculate bees. Despite an ancient association with their bee hosts, these symbionts are surprising dynamic over developmental, ecological and macroevolutionary time scales. I will discuss our recent discoveries of symbiont loss in bees, and efforts to understand why and how these losses occur."
Hammer received his bachelor's degree in general biology from UC San Diego in 2009 and his doctorate in evolutionary biology in 2018 from the University of Colorado, Boulder. He served as a postdoctoral researcher at the University of Texas, Austin, from 2018 to 2021.
Hammer's research interests include microbiomes, symbiosis, microbial ecology and evolution, bees, biodiversity, insect-plant interactions and tropical biology.
"We are a new research group at UC Irvine studying the ecology and evolution of symbioses between hosts (especially bees) and microbes," he writes on his lab website. His mission:
- To boldly venture into uncharted waters of symbiosis and bee biology, asking—and doing our best to answer—new questions about how they tick.
- To create a culture where lab members follow their curiosity, have fun, and regularly enjoy homemade baked goods.
- To contribute to making the academic community better reflect the diversity of society, and be a more welcoming, supportive place for historically marginalized scientists.
- To help wild bees, and connect people outside academia to insect biodiversity.
Hammer's most recent publications include
- Hammer, T.J., Le, E., Martin, A.N., Moran, N.A. 2021. The gut microbiome of bumblebees. Insectes Sociaux 68, 287-301.
- Silva Cerqueira, A.E., Hammer, T.J., Moran, N.A., Cristiano Santana, W., Megumi Kasuya, M.C., Canêdo da Silva, C. 2021. Extinction of anciently associated gut bacterial symbionts in a clade of stingless bees. The ISME Journal 15, 2813-2816.
- Hammer, T.J., Le, E., Moran, N.A. 2021. Thermal niches of specialized gut symbionts: the case of social bees. Proceedings of the Royal Society B 288, 20201480.
- Hammer, T.J., De Clerck-Floate, R., Tooker, J.F., Price, P.W., Miller, D.G., Connor, E.F. 2021. Are bacterial symbionts associated with gall induction in insects? Arthropod-Plant Interactions 15, 1-12.
- Hammer, T.J., Dickerson, J.C., McMillan, W.O., Fierer, N. 2020. Heliconius butterflies host characteristic and phylogenetically structured adult-stage microbiomes. Applied and Environmental Microbiology 86, e02007-20.
Nematologist Shahid Siddique, assistant professor, UC Davis Department of Entomology and Nematology, is coordinating the spring seminars. For Zoom technical issues, contact him at ssiddique@ucdavis.edu.
- Author: Kathy Keatley Garvey
She and other recipients of the prestigious President's Prize, (the first-place award), each held up an empty picture frame lettered with "Student Competition Winner."
Images from the ESA meeting are online on Flickr at https://www.flickr.com/photos/
Rutkowski delivered her 10-minute presentation on "Fungicide Impacts on Bumble Bees are Mediated via Effects on Bee-Associated Fungi" in the category, Plant-Insect Ecosystems: Ecology 3." She studies with community ecologist Rachel Vannette, associate professor, and is also advised by community ecologist and professor Rick Karban.
At the ESA's annual meetings, students are offered the opportunity to present their research and win prizes. They can compete in 10-minute papers (oral), posters, or infographics. First-place winners receive a one-year free membership in ESA, a $75 cash prize, and a certificate. Second-winners score a one-year free membership in ESA and a certificate.
Rutkowski's abstract:
"Native bees including bumble bees are important pollinators but face threats from multiple sources, including agrochemical application. Declining bumble bee populations have been linked to fungicide application, which could directly affect the fungi often found in the stored food and GI tract of healthy bumble bees. Here, we test the hypothesis that fungicides impact bee health by disrupting bumble bee -fungi interactions. Using two species, Bombus vosnesenskii and B. impatiens, we test the interactive effect of the fungicide propiconazole and fungal supplementation on the survival, reproduction, and microbiome composition of microcolonies (queenless colonies). We found that both bee species benefitted from fungi, but were differentially affected by fungicides. In B. vosnesenskii, fungicide exposure decreased survival while fungal supplementation mitigated fungicide effects. For B. impatiens, fungicide application had no effect, but fungal supplementation improved survival and offspring production. Fungicides altered fungal microbiome composition in both species, and reduced fungal abundance in B. vosnesenskii microcolonies, but not in B. impatiens, where instead fungal addition actually decreased fungal abundance. Our results highlight species-specific differences in both response to fungicides and the nature of fungal associations with bees, and caution the use of results obtained using one species to predict the responses of other species. These results suggest that fungicides can alter bee- fungi interactions with consequences for bee survival and reproduction, and suggest that exploring the mechanisms of such interactions, including interactions within bee-associated fungal communities, may offer insights into bumble bee biology and bumble bee conservation strategies. (Paper co-authors are associate professor Rachel Vannette, Eliza Litsey and Isabelle Maalouf)
Rutkowski completed her bachelor's degree at Cornell University, where she studied how the relationship between mycorrhizal fungi and their host plants impacts insect herbivores. On the Vannette lab website, she specifies that she studies "how bumble bees interact with the microbes, particularly fungi, in their environment, and how these relationships impact bee health."
Vannette describes her lab as "a team of entomologists, microbiologists, chemical ecologists, and community ecologists trying to understand how microbial communities affect plants and insects (sometimes other organisms too). We often study microbial communities in flowers, on insects or in soil. We rely on natural history observations, and use techniques from chemical ecology, microbial ecology and community ecology. In some cases, we study applied problems with an immediate application including pathogen control or how to support pollinators. Other questions may not have an immediate application but are nonetheless grounded in theory and will contribute to basic knowledge and conservation (e.g. how can dispersal differences among organisms affect patterns of abundance or biodiversity?)"
Related Information:
- Three UC Davis Graduate Students Win Top Awards at ESA Competition (Danielle Rutkowski, President's Prize; Maureen Page, second-place; and Kyle Lewald, second-place)
- UC Davis Graduate Students Present Their Research in ESA Competitions (Jill Oberski, Zachary Griebenow, Lacie Newton, Lindsey Mack, Danielle Rutkowski, Maureen Page, Xavier Zahnle, Erin Taylor Kelly, Jasmin Ramirez Bonilla, Madison Hendrick, Mia Lippey, and Gabriel Foote)
- Author: Kathy Keatley Garvey
“This is the first paper documenting induction/stimulation of pollen germination by non-plants,” said Christensen, a doctoral candidate in the Microbiology Graduate Group who joined the Vannette lab in January 2019. “Nectar-dwelling Acinetobacter bacteria, commonly found in flowers, stimulate protein release by inducing pollen to germinate and burst, benefitting Acinetobacter.”
The article, “Nectar Bacteria Stimulate Pollen Germination and Bursting to Enhance Microbial Fitness,” is online July 28 and will be in print in the Oct. 11th edition of the journal Current Biology.
Christensen, who co-authored the paper with community ecologist and associate professor Vannette, and former Vannette lab member Ivan Munkres, collected California poppies, Eschscholzia californica, from the UC Davis Arboretum and Public Garden, and Acinetobacter primarily from the Stebbens Cold Canyon Reserve, a unit the UC Natural Reserve System that encompasses the Blue Ridge Berryessa Natural Area in Solano and Napa counties.
The question—“How do organisms actually eat pollen?”--has been a long-standing one, Vannette said, “because pollen is well-protected by a layers of very resistant biopolymers and it's unclear how pollen-eaters get through those protective layers.”
“The finding that bacteria--in this case a specific genus of bacteria-- can cause premature pollen germination and release of nutrients-- is cool for a number of reasons,” said Vannette, a UC Davis Hellman Fellow. “First, Shawn's results are very novel--no one has described this phenomenon before! Second, Acinetobacter is a genus of bacteria that are very common in flowers. They are usually among the most abundant bacteria in nectar and are often found on other floral tissues, including pollen, stigmas etc.”
Christensen, an evolutionary biologist turned microbiologist, studies Acinetobacter and other nectar microbes and their potential influences on pollen for nutrient procurement, as well as the metabolomics of solitary bee pollen provisions.
The UC Davis doctoral student is a recipient of two research awards: the Maurer-Timm Student Research Grant, a UC Davis award for research conducted in the Natural Reserves; and a Davis Botanical Society research award, specifically for this project.
Shawn holds a bachelor of science degree in evolutionary biology from University of Wisconsin-Madison. “I studied reducing ecological impacts of phosphorus runoff, ethnobotany and domestication traits in Brassica rapa, botanical field excursions of all kinds, the evolution of chemical sets in the early origins of life, and now plant-microbe-pollinator interactions."
