Pollination ecologist Alexandra Harmon-Threatt, an associate professor at the University of Illinois, Urbana-Champaign, will speak on "Beyond Flowers; Examining the Role of Soils in Bee Conservation Efforts" at the next UC Davis Department of Entomology and Nematology seminar.
The online seminar, the last of the spring quarter, is set for 4:10 p.m., Wednesday, June 2. Host is pollination ecologist and professor Neal Williams. Access the Zoom link here.
More than 80 percent of bees nest below ground and most univoltine species spend more than 90 percent of their life cycle in contact with soils, Harmon-Threatt points out. "Yet most conservation efforts ignore soils and few research studies consider these critical life stages and possible exposures that occur during them. In a series of studies, our lab has begun to explore how much soils matter and whether ignoring them is to the detriment of conservation."
In her research, Harmon-Threatt zeroes in on understanding the patterns and processes that govern plant-pollinator interactions for conservation. "Pollinators play a vital role in plant reproduction, food production and ecosystem stability but are believed to be declining globally," she says. Her work focuses on identifying and understanding patterns in natural environments to help conserve and restore pollinator diversity. With a particular focus on bees, she investigates how a number of factors at both the local and landscape scale, including plant diversity, isolation and bee characteristics, effect bee diversity in local communities.
Harmon-Threatt received her doctorate from UC Berkeley, where she worked on bumble bee preferences and phylogenetic patterns. She completed a National Science Foundation postdoctoral fellowship in biology at Washington University in St. Louis.
She was recently featured on the podcast, People Behind the Science. Any change in pollinator populations, she told her audience, can have significant effects on natural and agricultural communities. Recent declines in bee populations, in particular, indicate how "little we know about these important insects in their natural environments, she told her audience."
The seminar, hosted by Professor Neal Williams begins at 4:10. Click here to register to attend.
Rader, an associate professor, says she is broadly interested in pollination ecology, landscape ecology and plant–animal interactions in natural and human-modified landscapes. She is currently working on projects that investigate the ways in which plant and animal biodiversity respond to global change and the performance of wild and managed insect pollinators in horticultural crops.
She writes on her website: "I am a community ecologist and my research focuses on plant–animal interactions in natural and human-modified landscapes. I am interested generally in the ecology of plants and animals in different types of habitats and landscapes and how they respond to differing management practices and global change. My current projects relate to wild and managed insect pollinators, their efficiency at pollinating horticultural crops and finding ways to improve fruit yield and quality by understanding their life history needs."
Rader holds a bachelor of environmental science (1998) from the University of New South Wales, Sydney, Australia. She obtained both her master's degree (2005) and doctorate (2011) from James Cook University, Cairns, Australia. Her master's thesis: "Vertical Distribution, Resource and Space Use in a Tropical Rainforest Small Mammal Community." For her doctorate: "The Provision of Pollination Ecosystem Services to Agro-Ecosystems by a Diverse Assemblage of Wild, Unmanaged Insect Taxa." She won a 2017- 2020 Australian Research Council Discovery Early Career Researcher Award.
Among her most recent journal publications:
- S.A.E.C. Wijesinghe, L.J. Evans, L. Kirkland & R. Rader 2020, ‘A global review of watermelon pollination biology and ecology: The increasing importance of seedless cultivars,' Scientia Horticulturae, vol. 271, pp. 109493,
- Heidi Kolkert, Rhiannon Smith, Romina Rader & Nick Reid 2020, ‘Insectivorous bats foraging in cotton crop interiors is driven by moon illumination and insect abundance, but diversity benefits from woody vegetation cover,' Agriculture, Ecosystems & Environment, vol. 302, pp. 107068,
- Jamie R. Stavert, Charlie Bailey, Lindsey Kirkland & Romina Rader 2020, ‘Pollen tube growth from multiple pollinator visits more accurately quantifies pollinator performance and plant reproduction,' Scientific Reports, vol. 10, no. 1,
- Liam K. Kendall, Vesna Gagic, Lisa J. Evans, Brian T. Cutting & Jessica Scalzo, Romina Rader. 2020, ‘Self-compatible blueberry cultivars require fewer floral visits to maximize fruit production than a partially self-incompatible cultivar,' Journal of Applied Ecology,
- Vesna Gagic, Lindsey Kirkland, Liam K. Kendall, Jeremy Jones & Jeffrey Kirkland Romina Rader 2020, ‘Understanding pollinator foraging behaviour and transition rates between flowers is important to maximize seed set in hybrid crops,' Apidologie,
Lead author Clara Stuligross, a doctoral student in the lab of pollination ecologist Neal Williams, a professor in the Department of Entomology and Nematology, teamed with Williams to study the results of food scarcity and pesticide exposure.
They exposed the bees to the neonicotinoid insecticide imidacloprid, widely used in agriculture, and found that the combined threats—imidacloprid exposure and the loss of flowering plants—reduced the bee's reproduction by 57 percent, resulting in fewer female offspring.
Of the two stressors—food scarcity and pesticide exposure—pesticide exposure showed the great impact on nesting activity and the number of offspring produced, they said.
The study, Pesticide and Resource Stressors Additively Impair Wild Bee Reproduction, accomplished in the spring of 2018 on the grounds of the UC Davis Harry H. Laidlaw Jr. Facility, is published in the journal Proceedings of the Royal Society B.
Other scientists have conducted similar research on honey bees, but this is the first comparable research on wild bees in field or semi-field conditions.
The blue orchard bee, nicknamed BOB, is a dark metallic mason bee, smaller than a honey bee. It is prized for pollinating almond, apple, plum, pear, and peach trees. California almond growers often set up bee boxes or bee condos for them in their orchards to aid in the honey bee pollination. In the wild, the bees nest in reeds or natural holes.
To study the survival, nesting and reproduction of the blue orchard bee, they set up nesting females in large flight cages, some with high densities of wildflowers and others with low densities that were treated “with or without the common insecticide, imidacloprid.” Bees are commonly exposed to insecticides when they forage on treated flowers.
"Understanding how multiple stressors interplay is really important, especially for bee populations in agricultural systems, where wild bees are commonly exposed to pesticides and food can be scarce,” said Stuligross, who holds a bachelor of arts degree in environmental studies (2014) from Earlham College, Richmond, Ind. She joined the UC Davis ecology doctoral program in 2016.
Onset of Nesting Delayed
Key factors in affecting bee reproduction are the probability that females will nest and the total number of offspring they have. The UC Davis research found that pesticide-exposed and resource-deprived female bees delayed the onset of nesting by 3.6 days and spent five fewer days nesting than unexposed bees.
Professor Williams pointed out that this is a substantial delay because bees nest only for a few weeks, and it's crucial to reproduce female offspring to carry on the future generations. “Fewer females will reduce the reproductive potential of subsequent generations," said Williams, a UC Davis Chancellor's Fellow and a newly elected fellow of the California Academy of Sciences.
They found that only 62 percent of pesticide-exposed bees produced at least one daughter compared to 92 percent of bees not exposed to pesticides.
The study drew support from a UC Davis Jastro Research Award, a UC Davis Ecology Graduate Research Fellowship, a National Science Foundation Graduate Research Fellowship, and the UC Davis bee biology facility
The blue orchard bee bee is one of the few native pollinators that is managed in agriculture. North America has 140 species of Osmia, according to a Pollinator Partnership (PP) article in a U. S. Forest Service publication, authored by entomologist and PP member Beatriz Moisset and PP director Vicki Wojcik. “Mason bees use clay to make partitions and to seal the entrance,” they wrote. “This unique mud-building behavior leads to their common designation as mason bees. Honey bees are very important to commercial agriculture, but native bees like the blue orchard bees are better and more efficient pollinators of native crops.”
Imidacloprid, a systemic insecticide that acts as an insect neurotoxin, is used to control sucking insects, termites, some soil insects and fleas on pets, according to National Pesticide Information Center. It mimics nicotine, toxic to insects, which is naturally found in many plants, including tobacco. More than 400 products for sale in the United States contain imidacloprid.
Winfree's webinar, “Do We Need Biodiversity for Ecosystem Services?” begins at 4:10 p.m. on Zoom at https://ucdavis.zoom.us/j/
All those interested can tune in--just click on the link, said Williams. "To access the talk, you do not need an account, but you will need to install zoom ahead of time. Use the link to join the meeting."
"Out of respect for the speaker, during the talk please keep your microphone muted, video off, and avoid using the chat feature," he added. "We will invite questions at the end."
Winfree says the goal of her research program is to understand the role of biodiversity in ecosystem services in the real world--that is, in large-scale and unmanipulated systems. We are developing a framework for thinking about this question that bridges the gap between smaller-scale experiments and the associated theory, which ecologists understand well, to the more complicated reality of nature. What is the most meaningful way to measure biodiversity in nature, and is the answer scale-dependent? Do we need to preserve biodiversity in order to maintain ecosystem services, or are only a few dominant species sufficient? What is the role of rare species in ecosystem services? Can we extend biodiversity-ecosystem function research to mutualist networks? These are some of our current questions."
As collaborators, Winfree and Williams recently published “Species Turnover Promotes the Importance of Bee Diversity for Crop Pollination at Regional Scales,” in the journal Science. They set out to answer the question: "How many wild bee species do we need to pollinate our crops?"
The answer, briefly: "Not nearly enough bees are available for crop pollination."
The UC Davis Department of Entomology and Nematology seminars, coordinated by community ecologist and assistant professor Rachael Vannette, are all virtual. Some have been cancelled and others postponed. See schedule.
- Lynn Kimsey, director of the Bohart Museum of Entomology and professor of entomology, UC Davis Department of Entomology and Nematology, whose expertise includes wasps. She is the "go-to" person in the department when the public requests general insect information.
- Neal Williams, professor and pollination ecologist, UC Davis Department of Entomology and Nematology, whose expertise includes native bees.
- Art Shapiro, distinguished professor of evolution and ecology, who has been monitoring the butterfly population of central California since 1972; and
- Brendon Boudinot, doctoral candidate and ant specialist, Phil Ward lab, UC Davis Department of Entomology and Nematology.
The society is inviting the public to "explore the world of insects as we bring together law and science to combat biodiversity decline and the sixth mass extinction," the co-chairs said. The all-day event, from 8:30 a.m. to 6:30 p.m. in the School of Law will take place in Room 1001. Registration is under way; see Facebook page.
The California Fish and Game Commission voted 3-1 on June 12, 2019 to place these four bumble bees on the proposed endangered species list, as petitioned by the Xerces Society, Center for Food Safety, and Defenders of Wildlife.
- Franklin's bumble bee, Bombus franklini
- Suckley cuckoo bumble bee, Bombus suckleyi
- Western bumble bee, Bombus occidentalis
- Crotch bumble bee, Bombus crotchi
An insect fair will take place during lunch time. Senior museum scientist Steve Heydon of the Bohart Museum will showcase pinned specimens and a live petting zoo. Also planned: research projects from the graduate students; sale of insect-themed t-shirts by the Entomology Graduate Student Association; and honey tasting from the UC Davis Honey and Pollination Center. Cricket protein bars will be handed out to all those interested.
"It should be a lot of fun for everybody," she said.
Sponsors, in addition to ELS, include the California Environmental Law and Policy Center; UC Davis John Muir Institute of the Environment and the UC Davis School of Law.
See agenda on the Facebook page.