- Author: Kathy Keatley Garvey
The top honors went to:
- Doctoral candidate Shawn Christensen and doctoral student Alexia "Lexie" Martin, both of the lab of associate professor and community ecologist Rachel Vannette, vice chair of the department; and
- Doctoral student Iris Quayle of the lab of professor and arachnologist Jason Bond, the Evert and Marion Schlinger Endowed Chair and associate dean, College of Agricultural and Environmental Sciences.
Christensen competed in the Plant-Insect Ecosystems (P-IE) Section, Apiculture; Martin in the P-IE Section, Pollinator Biology; and Quayle in the Systematics, Evolution, and Biodiversity (SysEB) Section, Biogeography.
Shawn Christensen. Christensen presented "Bee Specific! Solitary Bee (Anthophora bomboides) Hosts a Specialized Core Microbiome through Development."
His abstract: "Host-microbe interactions are important for the development and fitness of many macroorganisms. While social bees are dependent on a vertically transmitted gut microbiome, solitary bees, which comprise the vast majority of species diversity within bees, lack a specialized gut community. We explored the microbiome associated with the complete life cycle of the ground-nesting polylectic solitary bee Anthophora bomboides standfordiana, including bacterial and fungal composition and abundance. In contrast to expectations, we found that immature stages of this solitary bee maintain a distinct core microbiome consisting of Actinobacteria and one yeast species. Stage-specific shifts in microbial abundance and community composition occur most notably during bee diapause, during which the abundance of bacteria and fungi increased dramatically. We tested two adaptive hypotheses regarding the role of the microbiome in bee ecology. First, isolated brood cell Streptomyces strains were found to inhibit growth of multiple often pathogenic filamentous fungi, suggesting a role in pathogen protection during the long period of diapause. Second, sugar alcohol composition changed in tandem with major changes in microbial abundance suggesting links with bee metabolism or overwintering biology. Our results suggest that this Anthophora species hosts a conserved core microbiome that may provide key fitness advantages through larval development and overwintering. Much work remains to examine the nature of bee-microbiome ecology, but our study reframes the conditions thought to promote the evolution and maintenance of symbiosis."
Co-authors: Rachel Vannette and Sriram Srinivas, UC Davis; Quinn McFrederick, UC Riverside; Bryan Danworth, Cornell University; and Stephen Buchmann, University of Arizona
Her abstract: "Bees interact with and in some cases benefit from a diverse community of microbes, which can be obtained through intraspecific interactions or the environment. Due to differences in sociality, bee species vary in their main route of microbial acquisition and their dependence on microbes. Despite the observation that intraspecific transmission of microbes is imperfect and environmental microbes are nearly ubiquitous in flowers, the potential impacts of intraspecific versus floral microbes on overall pollinator health have not been evaluated. This study uses two model bee species - one social (Bombus impatiens) and one solitary (Osmia lignaria)--to assess the establishment and health impacts of floral and intraspecific microbes. 2x2 factorial experiments were performed on B. impatiens microcolonies and O. lignaria females to selectively introduce intraspecific microbes and/or floral microbes. Survivorship and reproduction were measured to assess bee health and fitness, and DNA extractions and amplicon sequencing were performed on bee guts to evaluate microbial establishment. The results of this study will inform how microbes from different acquisition routes establish in the host, shape the gut microbiome, and affect host health. Since many macroorganisms encounter both intraspecific and environmental microbes, this study provides a framework for similar work in other organisms."
Co-author: Rachel Vannette, UC Davis
Her abstract: "In the Namib Desert, one of the largest and oldest deserts, the genus Onymacris contains a rarity for darkling beetles (Tenebrionidae) – the presence of eight species with striking ‘white' elytra (ranging from stark white to tan/striped). This study seeks to examine the phylogenetic relationships among white Onymacris species to test whether multiple derivations of white elytra is due to convergence or introgression. Population genomic data (3RAD) was generated from all white species of Onymacris with intraspecific sampling for four widespread species (O. marginipennis, O. bicolor, O. candidipennis, O. langi cornelii). Phylogenetic trees were inferred from 995 loci using concatenated and coalescent-based methods. The analyses supported two clades: langi and bicolor each of which contain species with pure white elytra. Variational autoencoder (VAE) clustering analysis shows a pattern of genetically isolated populations (bicolor) and gene flow indicating introgression (langi). These analyses also infer a potential new Angolan species sister to O. marginipennis in need of evaluation. Ancestral character state and biogeographic reconstruction resolve the timing of white species' color expression against the backdrop of sand sea emergence and increased aridity in the Namib, a landscape renown for ‘pocket speciation' and an impressive amount of darkling beetle diversity accounting for nearly 80% of the known endemic beetle fauna. Dynamic coloration provides a fascinating system through which to examine the role of ecological pressures and evolutionary mechanisms but requires a phylogenetic framework to understand organisms' potential adaptations to extreme environments, which is increasingly vital in the face of global trends aridity trends."
Co-authors: Lisa Chamberland, James Starrett and Jason Bond, UC Davis
The full list of student winners--first, second and third places--is here.
Founded in 1889, ESA is the largest entomological organization in the world. Its more than 7,000 members are affiliated with educational institutions, health agencies, private industry, and government.
- Author: Kathy Keatley Garvey
The newly released video, titled “This Fly Torpedoes a Bindweed Bee's Nest,” appears on YouTube at https://youtu.be/gJHCoP4WqMc.
“Shawn has done a lot of work on this bee and with Deep Look, and he also leads our lab's work on Anthophora bomboides, a bumble bee mimic, and studies microbial associates of pollen and solitary bees,” said community ecologist and associate professor Rachel Vannette, a Chancellor's Fellow and vice chair of the Department of Entomology and Nematology.
The Deep Look crew filmed the bees, Diadasia bituberculata, in a nesting area outside the UC Davis Stebbins Cold Canyon Reserve, near Winters.
The bees, also known as digger bees or chimney bees, are specialists on bindweed, commonly known as morning glory. “The females use pollen only from one plant species and are active through the late spring and early summer,” said Vannette, an international leader in microbial ecology who studies interactions between plants, insects and microbes.
The video shows a female bee fly (family Bombyliidae) hovering over a nest entrance and dropping her eggs inside. The fly eggs hatch into larvae, which eat the bee larvae. Horizontal turrets with sideways entrances (also shown in the video) prevent the flyover egg drop.
Gabriela Quirós, coordinating producer of Deep Look and producer of this video, consulted with the UC Davis scientists, obtaining information on the location of the bee nests, as well as information on the brood cells, pollen, and turrets. The Deep Look production includes UC Davis images taken inside a bee nest.
Quirós also consulted with seven other scientists: Stephen Buchmann, University of Arizona; Andy Calderwood,Ventura County Deputy Agricultural Commissioner; Neal Evenhuis, Bishop Museum of Honolulu, Hawaii; Paul Havemann, UC Davis Natural Reserve System; Keng-Lou James Hung, University of Oklahoma; Doug Yanega, UC Riverside, and James Carey, a naturalist who researches and videos bindweed turret bees in the Santa Monica Mountains National Recreational Area.
Josh Cassidy, Deep Look lead producer and cinematographer, filmed all the footage except for the male bees fighting with each other (00;17;14- 00;25;22 in the video). James Carey, who filmed that footage, “has been regularly monitoring and filming bindweed turret bees since 2016 in Rancho Sierra Vista/Satwiwa, an open space in the Santa Monica Mountains,” Quirós said. “James also filmed the shot at 04;17-04;21 showing nests in the Santa Monica Mountains covered up at the end of the nesting season."
Evenhuis and Calderwood, both bee fly experts, identified the bee flies as Paravilla fulvicoma. “Neal explained the life cycle of these bee flies and advised me on the animation,” Quirós said. Deep Look editor and motion graphics expert Kia Simon created the animation of the bee fly larva eating the bee larva.
“How I got interested in producing an episode of Deep Look about bindweed turret bees was that Rachel Vannette told me about these bees in 2021,” Quirós related. “Rachel told me that Shawn Christensen, a doctoral student in her lab, was studying their pollen. Later, I saw on the Native Bees Facebook group, the videos that James Carey had recorded of bee flies dropping their eggs into the nests of bindweed turret bees in Rancho Sierra Vista/Satwiwa, in the Santa Monica Mountains. I hadn't known about bee flies until I saw his videos.”
“I became interested in trying to film a video about the interactions between bee flies and bindweed turret bees. I contacted Shawn Christensen in January of this year, and Shawn and I started checking in regularly to figure out when the bindweed bees would emerge. When they finally did come out in large numbers--they were later this year than usual--we were, luckily, ready to jump into action and film an episode.”
About 70 percent of the world's bee species are ground-nesting. “Females tirelessly scoop earth with their mandibles, softening it by dousing it with nectar they collected earlier,” Deep Look related. “They work side by side, but each is /queen/ of her own castle.”
More than 4,000 species of bee flies comprise the family Bombyliidae. “How do you tell a bee fly from a bee?” Deep Look asked. “Even though bee flies have hairy bodies like bees, if you look closely, you can tell them apart. Bee flies have big eyes that cover a large area of their heads. And bee flies' antennae are short compared to bees' antennae.”
- “The camera work is nothing short of amazing. Great job!” (Cassidy's photography equipment included a 100mm and 65mm macro lenses and a probe lens, a wide angle macro lens.)
- “Love the pollen pants, and I felt so bad for the bees whose hard work was spoiled by those pesky bee flies.”
- “This channel truly deserves much more recognition than it has, the amount of information and clear footage is marvelous.”
- "Thanks. It's not often I see a good short video on a native bee species or any native pollinator for that matter."
Christensen, a member of the UC Davis Microbiology Graduate Group and anticipating his doctorate in the spring of 2024, is an evolutionary biologist turned microbiologist. Christensen also researches other native bees, including Melissodes and Colletes.
Vannette focuses her research on the chemical and microbial ecology of plant-pollinator interactions and how microbes influence plant defense and resistance against insect pests. On its website, the Vannette lab is described 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.”
- Author: Kathy Keatley Garvey
Among previous recipients: Shawn Christensen of the Rachel Vannette lab, UC Davis Department of Entomology and Nematology, for research on how nectar microbes induce pollen germination to access scarce nutrients. (See Bug Squad blog)
Three to five grants of up to $2000 will be awarded for field-oriented botany projects in taxonomy, evolutionary biology, ecology, and/or floristics; or research projects related to the cultivation and propagation of succulents (or horticultural materials of these groups).
As part of the requirement of the funded projects, it is expected that plant voucher specimens and/or population samples will be obtained during the field component of the project and deposited in the UC Davis Center for Plant Diversity Herbarium or the UC Davis Conservatory as a return contribution, said Kate Mawdsley, chair of the Davis Botanical Society Student Grants Committee.
Grant recipients need to contact herbarium staff for information on the proper collection, preparation, and documentation of voucher specimens. Grant proposals must include the following information:
- Cover page. This page should include the project title, applicant's name, applicant's current position, UC Davis campus address, telephone number, and e-mail address. The applicant should also include the name of their faculty advisor and provide contact information. Collaborators, if any, should be identified on the cover page and their roles in the project briefly described.
- Proposed project description. The project description should include a statement of significance of the research, objectives, hypotheses to be tested, materials and methods, anticipated results, expected completion date, and plans for collection and disposition of voucher specimens. The project description should be no longer than three typewritten pages, single-spaced (12-point font size, one-inch margins).
- Applicant's qualifications to carry out the proposed research. Briefly explain why you are well-prepared to complete this project with a good chance of success. If the applicant has received a previous award from the Davis Botanical Society, a one-page summary of the results and an accounting of the funds are required.
- Proposed budget. Grant funds are intended only for travel expenses, appropriate and necessary equipment, and expendable supplies. The funds are not for salaries. Please include name and e-mail address of the accounts manager in the applicant's home department so the funds can be distributed properly.
- Letter of recommendation. If the project is being carried out under the guidance of a faculty advisor, the advisor should be identified and asked to submit a letter of recommendation directly to the selection committee at the e-mail address below. Otherwise, a letter of recommendation should be sought from a researcher familiar with the applicant's abilities and proposed research, and submitted by the letter writer to the e-mail below.
Application materials (except for the letter of recommendation) must be submitted electronically as a single PDF document titled with the Applicant's Last Name and DBS Proposal 2023 by 5 p.m., Monday, March 6, 2023. Please send to the chair of the Davis Botanical Society Student Grants Committee, Kate Mawdsley, as an e-mail attachment to wfm-kfm@pacbell.net. Applicants will be notified by early April if they are a grant recipient.
The Davis Botanical Society is the support organization for two UC Davis botanical collections that benefit all Californians: the UC Davis Center for Plant Diversity and the Botanical Conservatory. Membership benefits include a subscription to the semi-annual newsletter, Lasthenia (name relates to the goldfields in the botanical family Asteraceae). Membership benefits also include invitations to talks, field trips, and other events, as well as a substantial discount on the price of field trips and classes.
- 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."