- Author: Kathy Keatley Garvey
The seminar also will be virtual. The Zoom link is https://ucdavis.zoom.us/j/3661107142.
Stuligross researches nutrition and pesticide exposure and their comparative effects on the blue orchard bee, Osmia lignaria, and the yellow-faced bumble bee, Bombus vosnesenskii. Pollination ecologist Neal Williams, professor in the Department of Entomology and Nematology, served as her major professor.
"I am doing a short postdoc with Neal Williams this fall, and in January I will start a postdoctoral research position with Nicole Rafferty at UC Riverside," Stuligross said.
"Anthropogenic environmental changes present multiple stressors that together impact biodiversity and ecosystem function," Stuligross writes in her abstract. "Among these, pesticide exposure and the loss of flowering plants are ubiquitous across contemporary landscapes and threaten the persistence of bee populations. In this dissertation, I explored the individual and combined effects of pesticide and floral resource stressors on bee behavior, reproduction, and population persistence, as well as a potential strategy for mitigating these impacts. I used a combination of manipulative field cage experiments and landscape studies to examine these stressors and their impacts at different scales.
"Because bees often experience pesticide and resource stressors simultaneously, I first examined the potential for interactive effects of these stressors, as well as their individual impacts on wild bees. I established a fully crossed design in field cages; nesting female Osmia lignaria, the solitary blue orchard bee, accessed wildflowers at high or low densities, treated with or without the common insecticide, imidacloprid. In Chapter 1, I showed that pesticide exposure and floral resource scarcity combined additively to dramatically alter multiple vital rates, including reduced reproduction and a male-biased offspring sex ratio. In Chapter 2, I quantified behavioral responses in the same experiment, revealing that the resource and pesticide stressors had differential impacts with consequences for bee populations and potentially for pollination services through individual behavioral changes. Limited floral resources required bees to make fewer, longer foraging trips as well as misidentify their nests more often upon return from these trips. Bees exposed to pesticides made shorter foraging trips and did not compensate for this by taking more trips, reducing their overall foraging activity. Pesticide exposure also interacted with age to affect antagonistic behavior."
"In Chapter 3, I examined the carryover effects of past pesticide exposure on wild bees. Using the offspring from the previous cage experiment with known pesticide exposure backgrounds, I re-established the field cages and released bees in a crossed design with pesticide exposure or no exposure in each year. Thus, some bees experienced pesticides over two generations and others not at all. Regardless of the past exposure history, pesticides in the second year reduced reproduction. For bees that were also exposed in the past, the exposure over two years additively impaired individual performance, leading to a nearly fourfold estimated reduction in bee population growth. Furthermore, even past exposure by itself, regardless of exposure in the second year, led to a decline in offspring production."
"In Chapter 4, I collaborated with Maj Rundlöf to investigate the potential for wildflower plantings to mitigate the negative effects of pesticide exposure in agricultural landscapes. We assessed the nesting and reproduction of O. lignaria and the bumble bee Bombus vosnesenskii in replicate agricultural landscapes, half of which contained a wildflower planting next to the nest or colony. We collected pollen from foraging bees to determine resource use and pesticide residues. The wildflower plantings were a source of pesticide exposure, especially for O. lignaria, but also supported O. lignaria nesting. The landscape-level floral resources better predicted B. vosnesenskii colony success, but the local flower resources mitigated the negative effects of pesticides on their reproduction."
"These chapters together show that two common environmental stressors combine to negativel impact bees. They also reveal potential mechanisms underlying impacts of the stressors on reproduction and population growth. My dissertation highlights the importance of mitigating the negative effects of pesticides and floral resource limitation, especially in agricultural landscapes where the two stressors often co-occur. Finally, this work offers insight into how the stressors could be mitigated through an emerging strategy to diversity agricultural landscapes."
Stuligross received her bachelor of arts degree in environmental studies in 2014 in Indiana from Earlham College, Richmond, where she minored in biology and outdoor education. At UC Davis, she was awarded a 2017-22 National Science Foundation Graduate Research Fellowship, and a 2016-18 UC Davis Graduate Group in Ecology Fellowship.
Recognized nationally for her research, Stuligross scored second place in the Entomological Society of America's 2020 President's Prize competition. Her research posters also won the top award at the UC Davis Graduate Student Symposium in Ecology in both 2019 and 2021.
Stuligross and her colleague, Maj Rundlöf, are the co-first authors of "Flower Plantings Support Wild Bee Reproduction and May Also Mitigate Pesticide Exposure Effects," published in May 2022 in the Journal of Applied Ecology. She was the lead author of "Past Insecticide Exposure Reduces Bee Reproduction and Population Growth Rate," published in November 2021 in the Proceedings of the National Academy of Sciences, and also the lead author of "Pesticide and Resource Stressors Sdditively Impair Wild Bee Reproduction," published in September 2020 in The Proceedings of the Royal Society B.
Stuligross has also co-authored a number of other research publications, most recently:
- "A Meta-Analysis of Single Visit Pollination Effectiveness Comparing Honeybees and Other Floral Visitors," American Journal of Botany
- "Impact of 'Nonlethal' Tarsal Clipping on Bumble Bees (Bombus vosnesenskii) May Depend on Queen Stage and Worker Size," Journal of Insect Conservation
- Author: Kathy Keatley Garvey
The study suggests that wild bee populations likely declined in areas comprising 23 percent of the nation between 2008 and 2013, a decline associated with conversion of natural wild bee habitat into intensive agriculture.
The paper, titled “Modeling the Status, Trends and Impacts of Wild Bee Abundance in the United States,” is published today (Dec. 21) in the Proceedings of the Natural Academy of Sciences.
The seven-member team, led by Insu Koh of the Gund Institute for Ecological Economics at the University of Vermont, Burlington, integrated a wild bee habitat model, land cover data and expert knowledge to map U.S. bee abundance and trends. Pollination ecologist Neal Williams of UC Davis led efforts to assess habitat quality.
Wild bees and pollination demands
“We see striking mismatches in many places between the demand for pollination and the ability of wild pollinators to support that need,” said Williams, an associate professor in the UC Davis Department of Entomology and Nematology, who helped design the study and led efforts to assess bee habitat quality as part of the Integrated Crop Pollination (ICP) Project (http://icpbees.org/.
“Indeed it is crops where demand has most increased that we estimate greatest decline in wild pollinator supply,” Williams said.
“The research is also unique in including uncertainty in our knowledge of the quality of habitat for pollinators and thus recognizes where more effort is needed to understand the vulnerability of pollination services,” he added.
Williams noted that the paper has the potential to bring wider attention to the correlation between the status of wild bee communities and crop pollination demands nationally.
Mismatch in pollination supply and demand
The researchers determined that 139 key counties, comprising 39 percent of U.S. pollinator-dependent crop area, exhibit a “mismatch between pollination supply and demand,” with large areas of pollinator-dependent crops and low expected abundance of wild bees.
The authors noted that the supply of managed honey bees has not kept pace with pollination demand and needs, due to management challenges and colony loss over the last decade. “There is growing evidence that wild, unmanaged bees can provide effective pollination services where sufficient habitat exists to support their populations,” they wrote.
“Until this study, we didn't have a national mapped picture about the status of wild bees and their impacts on pollination,” Koh said. More than $3 billion of the U.S. agricultural economy depends on the pollination services of native pollinators like wild bees.
Some of the most important crop pollinators are bumble bees, which have declined over the past decades. “Our mapped index of bee abundance clearly shows that areas of intense agriculture (e.g. the Midwest Corn Belt and California's Central Valley) are among the lowest in predicted wild bee abundance,” the authors pointed out.
Helping agriculture preserve wild pollinators
The authors agreed that the study results may help farmers and agricultural stakeholders develop management efforts to preserve wild bee populations and their pollination services in farmland. Just like honey bees, wild bees are important pollinators and face many of the same threats including habitat loss, environmental pesticide exposure, and climate change.
In addition, the results may help wild bee researchers focus attention on poorly understood regions, the authors said.
Responding to White House call
The study comes on the heels of a 2014 U.S. presidential memorandum calling for a national assessment of pollinators to promote the health of honey bees and other pollinators. One goal is to set aside 7 million acres over a five-year period for pollinators.
Williams said that the modeling study provides important information. “Such assessment is highly valuable in response to calls at the federal level (the White House memorandum and resulting agency responses) to direct research and management efforts to wild pollinators,” he said. “I really hope the paper will generate additional original efforts to improve our understanding of the challenges facing pollinators and their critical role in sustainable food supply.”
Collaborators:
The team also included Claire Brittain of the Neal Williams lab, UC Davis Department of Entomology and Nematology; Taylor Ricketts of the Gund Institute and the University of Vermont; Eric Lonsdorf of Franklin and Marshall College, Lancaster, Pa.; and Rufus Isaacs and Jason Gibbs of Michigan State University, East Lansing.
The study was completed with support from the Specialty Crop Research Initiative of the U.S. Department of Agriculture's National Institute for Food and Agriculture.
Contact:
Neal Williams
nmwilliams@ucdavis.edu
(530)-752-9358
Related Links:
PNAS Online
Online News Release from University Vermont
- Author: Kathy Keatley Garvey
Williams will receive an award of $25,000 to be used in support of his research, teaching and public service activities. He will serve as a Chancellor's Fellow until July 1, 2020, Katehi said.
The program, established in 2000 to honor the achievements of outstanding faculty members early in their careers, is funded in part by the Davis Chancellor's Club and the Annual Fund of UC Davis.
His research focuses on the ecology and evolution of bees and other pollinator insects and their interactions with flowering plants, especially in light of changing landscapes. His work is particularly timely given concern over the global decline in bees and other pollinators.
Colleagues praise him for being a gifted scientist doing groundbreaking fundamental research and as an effective communicator of research findings to California agriculture, especially the almond industry.
Williams joined the UC Davis faculty in 2009 and received tenure as an associate professor in 2013. He received his doctorate in evolution and ecology from State University of New York, Stony Brook.
More information on the Fellows, from Dateline