Newly published UC Davis research, the first of its kind, reveals that pesticide exposure and food scarcity pack a double punch to blue orchard bees, Osmia lignaria, a wild  bee that pollinates early spring bloom, including almonds. 

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. 

“Bees and other beneficial insects experience multiple stressors within agricultural landscapes that act together to impact their health and diminish their ability to deliver the ecosystem services on which human food supplies depend,” they wrote in their abstract. “Disentangling the effects of coupled stressors is a primary challenge for understanding how to promote their populations and ensure robust pollination and other ecosystem services.” 

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.   

“Pesticides and resource limitation acted additively to dramatically reduce reproduction in free-flying bees,” they wrote in their abstract. “Our results emphasize the importance of considering multiple drivers to inform population persistence, management, and risk assessment for the long-term sustainability of food production and natural ecosystems.” 

"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.

Professor Rachael Winfree of Rutgers University, New Brunswick, N.J., who does "innovative work in biodiversity, ecosystem services and global environmental change," will present a virtual UC Davis Department of Entomology and Nematology seminar on Thursday, May 14, announced host Neal Williams, UC Davis professor of entomology and a Chancellor's Fellow.  

Winfree's webinar, “Do We Need Biodiversity for Ecosystem Services?” begins at 4:10 p.m. on Zoom at https://ucdavis.zoom.us/j/93312644886.

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. 

Four UC Davis entomologists will be among the speakers when the UC Davis Environmental Law Society (ELS) sponsors a  public symposium on "Saving a Bug's Life: Legal Solutions to Combat Insect Biodiversity Decline and the Sixth Mass Extinction" on Friday, March 6  in the School of Law.

They are:

• 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.

Neal Williams, professor of entomology (Photo by Kathy Keatley Garvey)

Insects have been called "the level pullers of the world." One study estimates that insects contribute more than $57 billion a year to the U.S. economy. However, many species currently face extinction. The symposium will bring together  law and science to address biodiversity decline. Experts in the field of entomology and agricultural sciences will converse with leaders in government, legal scholars and practitioners about the current threat to insect populations "and how we can use legal tools, policy and management practices to combat the sixth mass extinction," according to symposium co-chairs Kelly Beskin (kvbeskin@ucdavis.ed) and Peter Jansen (pcjansen@ucdavis.edu).

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.

Some of the major topics will be about "listing insects under the Endangered Species Act and the tensions within agriculture between the need for pollinators and pesticide use," said Beskin.

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.

"Why Are the Monarch Butterflies Declining in the West?"

When Professor Elizabeth Crone of Tufts University, Medford, Ma., zeroes in on that topic to the UC Davis Department of Entomology and Nematology, she will discuss the challenges that both monarchs and ecologists face.

Her seminar is from 4:10 to 5 p.m., Wednesday, Jan. 29 in 122 Briggs Hall. Her longtime collaborator, pollination ecologist and professor Neal Williams, will introduce her.

"Ecologists now face the dual challenge of documenting changes in the environment, and figuring out appropriate strategies for conserving and recovering natural resources in changing environments," says Crone, who is completing a research sabbatical at UC Davis.

In her talk, she will focus on “using the tools of population ecology to address both sides of this challenge: quantifying changes in the abundance of western monarch butterflies (and factors associated with these changes), and using theory and data to design strategies and targets for restoration and recovery.”

“Analyses of past dynamics (1980-2017) showed that western monarch butterflies have declined more quickly than their eastern counterparts, and that these declines were most strongly associated with loss of overwintering habitat, and more weakly (but significantly) associated with increased pesticide use and warmer breeding season temperatures,” Crone writes in her abstract. “Analyses of current conditions (2018-2019) suggest that a recent dramatic drop in abundance occurred in spring, between when monarch butterflies leave coastal overwintering sites and arrive in the Central Valley and Sierra Foothills.”

“Surprisingly, we don't really know where western monarch butterflies are during this time period, roughly mid-February through mid-May," Crone says.  "Future research will focus on filling this knowledge gap, as well as building quantitative knowledge of the western monarch demography throughout their complex annual life cycle, which is needed to understand the relative contributions of habitat at different points in the life cycle to population declines and recovery.” 

The Xerces Society for Invertebrate Conservation reported this week that its Western Monarch Thanksgiving Count shows a decline for the second consecutive year. “Sadly, fewer than 30,000 monarchs were counted—29,418 to be exact—for the second year in a row, so the western monarch population remains at a critical level,” according to Matthew Shepherd, director of communications and outreach.  (See press release and a blog article about the population count for this winter.)

A native of Alexandria, Va., Crone received her bachelor's degree in biology, summa cum laude, from the College of William and Mary, Williamsburg, Va., in 1991, and her doctorate in botany from Duke University in 1995. She served as a postdoctoral researcher at the University of Washington, Seattle, from 1996-1997. Her career encompasses academic appointments at Harvard University, University of Montana, and the University of Calgary.

No stranger to UC Davis, Crone has collaborated with Neal Williams "on and off" for the past 20 years.  “We had a National Science Foundation grant to study bumble bee populations from 2014-2019, so I have been visiting regularly since he got here.  Starting in winter 2019, I have also had funding to take partial research leave from Tufts and work on western monarchs.  I have been about half-time at Tufts and half-time at UC Davis."

"I am grateful to Neal and the Entomology Department for hosting me during this extended stay!" she added.

Crone is a co-principal investigator (PI) with PI Cheryl Schultz, associate professor of biological sciences at Washington State University  and co-PI Sarina Jepson, endangered species program director, Xerces Society, on a federal grant, "Western Monarch Breeding Phenology" (awarded May 2017-June 2020, with the potential for annual renewal). The grant was funded through the Department of Defense's (DoD) Natural Resources Program, DoD Legacy Program.

Of her research, Crone says "My research focuses on population ecology, especially of plants and insects, and plant-animal interactions. Specifically, I am interested in how environmental changes translate to changes in population dynamics: For example, is there a simple, linear matching of changes in resources to abundance of consumers, or do interactions among individuals and species moderate these responses? Much of my research also involves developing novel quantitative approaches to predict long-term dynamics from small scale observations and experiments. Current projects include studies of butterflies, bees, perennial wildflowers, sugar maples, and acorn-granivore interactions. Past projects include some of the best documented examples of cyclical dynamics in plant populations and spatial metapopulation dynamics in animal populations. I was also one of the first ecologists to adapt generalized linear mixed models to estimate variance terms for stochastic population models."

Of her teaching: "I am interested in introducing people to general principles of ecological theory, as a guide to interpreting data and understanding the potential implications of environmental change. Making this link requires training students to understand basic biology and natural history, while knowing how to approach problems like a mathematician. I have a strong track record of training graduate students who have gone on to work in quantitative ecology, and in teaching lecture courses that introduce biology students to modeling and statistics. In biology classes, students expect to understand material as it is presented in class, and use time outside class to explore these ideas further, or memorize facts. In math classes, students do not expect to understand the material as it is presented; many of the best math majors come to understand the ideas later by working through problem sets. This difference means that biology students find math classes intimidating and tend to underestimate their own math skills. My approach is to start with tractable problems, and introduce students to the approach of learning by doing problem sets, in the context of ecologically-motivated problems."

Her honors and awards are many:

• Project of the Year Award, SERDP (Strategic Environmental Research and Development Program)  2018
• Foreign Member, Finnish Academy of Science and Letters (elected 2017)
• Vice Chair / Chair, Theoretical Ecology Section, Ecological Society of America, 2010-2012
• Ecological Research Award, Ecological Society of Japan, 2014
• Fulbright Fellowship, 2007-2008
• National Science Foundation (NSF) Postdoctoral Fellowship in Biosciences Related to the Environment (1996-1997)
• U.S.Department of Energy Graduate Fellowship for Global Change (1991-1995)
• Baldwin Speece Award (College of William and Mary, for scholarship/service in ecology, 1991)

Some questions:  

How did you get interested in science? Was there an "ah ha" moment? 

I was in an REU (Research Experiences for Undergraduates) program studying plant-insect interactions in 1990.  The thing that made me want to go to grad school was the fun puzzle of designing an experiment AND figuring out how to interpret the data - I had collected data on beetle feeding rates, and when I didn't know how to analyze them my advisor said "read a statistics book" ... so I did--since then I have always especially loved the puzzle of matching models to data. 

From an earlier age, I have always enjoyed being outdoors, which is probably why I chose to study biology.  But that was the moment when I knew I would enjoy a life of research. 

Some of your major accomplishments?

From an applied ecology perspective, the biggest is helping the Fender's blue butterfly move from being listed as endangered to nearly ready for down-listing.  From a basic ecology perspective, I figured out the ecological interpretation of variance terms in mixed models as estimates of spatial heterogeneity and environmental stochasticity, and worked out one of the best examples of how mast-seeding species are synchronized by their pollinators.  

What fascinates you about monarchs?

The possibility that we can recover the western monarch population from its recent steep decline to being abundant again.  This should be a problem we can fix. 

What do you like best about science?

The puzzle of matching models to data and the possibility of saving species from extinction. 

Any scientists in the family?

My sister is an astronomer.  My dad was a math professor.  Before him, though, no one in the extended family had even gone to college.   

What do you do in your leisure time? 

I once gut-renovated a house (with help from carpenters, but doing some of the work myself), I am very proud of my urban pollinator garden in Somerville (near Boston, Mass., and I am a good enough trombonist to (just barely) keep up with my trombonist friends.

Future plans?

I am waiting to find out whether our monarch funding will be extended or whether I will go back to a regular teaching schedule at Tufts.  Even if I go back to "full-time" teaching, I am sure I will be doing western monarch and bumble bee research for the indefinite future, and will continue to be at least partly bicoastal.

(Editor's Note: the Xerces Society's site-by-site monarch count data is available at https://www.westernmonarchcount.org/data/. This covers all years since the first count in 1997.)