- Author: Kathy Keatley Garvey
if you hike a short distance up a meandering trail, you'll see a landscape of turrets, the work of solitary, ground-nesting digger bees, Anthophora bomboides standfordina.
The nests remind us tiny sandcastles. The female bees did that!
In the early spring you'll see the bees nectaring on wild radish and other flowers.
These digger bees are found along the sandy cliffs of beaches along the Pacific Coast, not just Bodega Head. They're sometimes called the “Stanford bumble bee digger” because its subspecies name, “stanfordiana,” refers to a 1904 Stanford University collection.
They are bumble bee mimics; they mimic the yellow-faced bumble bee, Bombus vosnesenskii.
It was Robbin Thorp (1933-2019), distinguished emeritus professor, UC Davis Department of Entomology and Nematology (ENT), who alerted us to them. He studied them at the Bodega Marine Reserve and loved to share his research.
So, on every trip to the Bodega Head, we scramble up the trail to see what the bees are doing. Of course, when they're overwintering, we don't see them at all, just the turrets.
Fast forward to today. On the ENT website, we posted a research story today that began 'Microbes found in the immature stages of a solitary bee that nests in sand cliffs along Pacific Coast beaches may be helping the bee defend itself from pathogens and protect it from cold stress, according to newly published research led by microbiologist Shawn Christensen of the Rachel Vannette Lab, UC Davis Department of Entomology and Nematology."
The research publication, “Symbiotic Bacteria and Fungi Proliferate in Diapause and May Enhance Overwintering Survival in a Solitary Bee,” appears in the current issue of the journal, International Society for Microbial Ecology (ISME), and is posted on the National Library of Science website.
“Contrary to what has previously been assumed and found in other systems, we found that dormant--also called diapausing--bees have more abundant symbiotic bacteria and fungi,” said Christensen, a doctoral candidate and the 2024 recipient of the Merton Love Ecology and Dissertation Award, an annual award that celebrates the university's most outstanding doctoral dissertation in the fields of ecology and evolutionary biology. He's scheduled to receive his doctorate this month.
The six-member research team, including colleagues from Cornell University, UC Riverside and the University of Arizona, also found “that the microbiome of this solitary bee is very consistent--the same taxa appear in most brood cells, in similar proportions,” said Christensen. “This is uncommon in solitary species, which normally have variable microbiomes due to lack of social transmission. We are still exploring this unique aspect!”
Vannette, associate professor and vice chair of the department and an international leader in microbial ecology, researches interactions between plants, insects and microbes. She is a principal investigator of a National Science Foundation grant that funded the project.
“Previous work on bee-microbe interactions has shown how gut bacteria benefit honey bees and other corbiculate social bees but these microbes are limited to social bees,” Vannette told us. “We wondered if solitary bees also associate with beneficial microbes and uncovered this previously undescribed partnership between bees, fungi and bacteria. This study opens up new questions in bee ecology and host-microbe interactions: how do solitary bees maintain specific associations with bacteria and fungi? What chemistry are Streptomyces using to suppress fungi? Does this association benefit bees? We think it is likely but ongoing work will examine these questions.”
“We are also thrilled to find this unique symbiosis in a bee species that has been well-studied by previous faculty at UC Davis, including RobbinThorp,” Vannette said. “UC Davis nematologist Harry Kaya, with graduate student Robin Giblin, also described Bursaphelenchus seani, a nematode that inhabits Anthophora bomboides. Our lab is also investigating links between the brood cell microbiome and the nematodes in this bee species.”
Other co-authors of the paper are
- Quinn McFrederick, assistant professor at UC Riverside who studies symbionts (pathogens, commensals, and mutualists) of wild and solitary bees
- Bryan Danforth, professor at Cornell University, who specializes in bee systematics and evolution
- Stephen Buchmann, pollination ecologist affiliated with the Departments of Entomology and of Ecology and Evolutionary Biology at the University of Arizona
- Sriram Srinivas, then a UC Davis undergraduate researcher in the Vannette lab
Check out Thorp's presentation on digger bees that he delivered at the “Proceedings of the Symposium on Biodiversity of Northwestern California” in October, 1991, in Santa Rosa.
Also check out the wonderfully done PBS Deep Look Video, This Bee Builds Sandcastles at the Beach.
Let's dig the digger bees.
- Author: Kathy Keatley Garvey
Free and family friendly, the open house takes place from 1 to 4 p.m. in Room 1124 of the Academic Surge Building, 455 Crocker Lane, UC Davis campus.
"It should be a great event!” said Tabatha Yang, education and outreach coordinator. “There is a lot of interest in bees this time of year. The format will be tabling with direct conversations with visitors.” The event is free and family friendly. Parking is also free.
Among those participating will be the laboratory of community ecologist Rachel Vannette, associate professor and chair of the UC Davis Department of Entomology.
"At the Vannette Lab booth, you will be able to look into the life of a bee--both in terms of where they live and how they develop!" said doctoral candidate and researcher Lexie Martin. "A live bumble bee nest and solitary bee nests will be available, so you can peer inside a bee's house! Additionally, there will be live bee larvae to observe under a microscope and interactive displays on the bee life cycle."
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."
Vannette's lab members participating at the open house will include:
Lexie Martin, doctoral candidate in the Entomology Graduate Group. She is interested in the impact of microbes on bee health
Dino Sbardellati, doctoral student in the Microbiology Graduate Group. He is a microbiologist interested in understanding how microbial ecology shapes macroscale ecology
Leta Landucci, a junior specialist and biochemist. She is inspired by chemical ecology, and broadly interested in exploring chemically mediated plant-insect-microbe interactions
Others scheduled to participate are Bohart Museum scientists and bee specialists Thomas Zavortink and Sandy Shanks; doctoral student Sofía Meléndez Cartagena of the Stacey Combes lab, Department of Neurobiology, Physiology and Behavior (she will focus on local bee diversity); Chancellor's Fellow Santiago Ramirez, associate professor, Department of Evolution and Ecology, who studies orchid bees; doctoral student Peter Coggan of the Ramirez lab (Coggan studies the neurological and genetic basis of orchid bee courtship behavior and evolution); and Richard Martinez, entomology graduate student researcher in the lab of apiculturist Elina Niño,associate professor of Cooperative Extension, UC Davis Department of Entomology and Nematology.
Martinez says that the E.L Niño Lab booth will display an observation hive and offer honey tasting from a variety of floral sources. He will be sharing recent projects aimed at improving honey bee health via dietary supplements. He also plans to showcase beekeeping suits and hive tools.
UC Davis distinguished professor emerita Lynn Kimsey, who directed the Bohart Museum for 34 years, is also scheduled to participate. She is known as "wasp woman," but she did her dissertation on orchid bees in Panama.
The Bohart Museum houses a global collection of eight million insects, plus a live petting zoo, and a gift shop. Professor Jason Bond directs the museum as of Feb. 1, succeeding UC Davis distinguished professor emerita Lynn Kimsey, who served 34 years. Bond is the Evert and Marion Schlinger Endowed Chair of the Department of Entomology and Nematology, and the associate dean, UC Davis College of Agricultural and Environmental Sciences. He also serves as president-elect of the American Arachnological Society.
For more information, access the website at https://bohart.ucdavis.edu or contact bmuseum@ucdavis.edu.
- Author: Kathy Keatley Garvey
A member of the Microbiology Graduate Group and the laboratory of community ecologist Rachel Vannette, associate professor and vice chair of the UC Davis Department of Entomology andNematology, he will deliver the Merton Love seminar from 3 to 4:30 p.m., Friday, May 24 in Room 1230 of Walker Hall. The Zoom link:
https://ucdavis.zoom.us/j/99429777483.
The award memorializes Robert Merton Love (1909-1994), emeritus professor of agronomy and range science, who served on the UC Davis faculty from 1940-1976.
“Shawn's thesis work spans microbiology, ecology and evolutionary biology, combined with careful natural history, to document novel species interactions between hosts and microbial communities,” said Vannette, who nominated him for the award. “Each chapter has broad implications for the ecology and evolution of host-microbe interactions. Shawn's work has already reframed the conditions under insect-microbe interactions are thought to hold relevance and evolve. His research has highlighted the utility of natural history observations of microbes and sampling understudied life history stages (overwintering developing insects).”
“Overall, Shawn's dissertation is an example of how detailed observations combined with fearless experimental dissection of interesting phenotypes can yield novel descriptions of species interactions that change the field's perception of when and where microbial communities are important,” she said.
“Shawn's first chapter describes adaptations of a flower specialist bacteria to acquiring resources from pollen—a nutrient source specific to flowers,” Vannette said. “Our lab was interested in the ecology of the flower-dwelling bacteria Acinetobacter, but Shawn took a new look at this bacterium, examining its growth morphology in nectar and in association with pollen. He noticed that this bacterium co-localized with pollen and grew exponentially more in the presence of pollen. To explore this phenotype, he designed new media and assays (microwaving pollen) to determine that Acinetobacter benefits the most from live pollen via stimulating pollen to germinate (within minutes!), then digesting it. Shawn then designed a series of experiments to examine if this ability was unique to this bacterial clade or shared among many floral microbes (it seems to be specific to Acinetobacter).”
“He collected brood cells (nectar and pollen balls along with developing larvae) from these locations at multiple points through bee development and examined not only the bacteria and fungal community composition through insect development, but also examined changes in microbial abundance at each life stage,” Vannette said. “In contrast to my (and the literature's) predictions, Shawn showed that microbial abundance peaks during larval overwintering, when solitary bees and other holometabolous insects are predicted to have voided their microbial gut communities. Instead, healthy A. bomboides hosts the highest abundance of fungi and bacteria during the fall—a wet season where pathogen abundance is also highest.”
Christensen received accolades and widespread media coverage for the first chapter of his dissertation, “Nectar Bacteria Stimulate Pollen Germination and Bursting to Enhance Microbial Fitness,” published in July 2021 in Current Biology. His second thesis chapter on the microbes associated with Anthophora bomboides, has just been accepted for publication by the International Society of Microbial Ecology (ISME).
And more good news: Christensen is a" co-principal investigator on a newly awarded grant by JGI to sequence the genome of the yeast," Vannette said, "and explore its functional potential in renewable energy and is applying to continue to leverage this system's potential in antifungal chemistry and evolution of pathogen defense.”
Every time we see the nests of Anthophora bomboides stanfordiana on the sand cliffs at Bodega Head, we think of the scientists, including Shawn Christensen and Rachel Vannette, who study them. The late Robbin Thorp, UC Davis distinguished emeritus professor, UC Davis Department of Entomology and Nematology, researched them decades ago.
Check out PBS' Deep Look video, "This Bee Builds Sandcastles at the Beach," and you'll never go to Bodega Bay without thinking of these digger bees.
/span>- Author: Kathy Keatley Garvey
The schedule:
Saturday, Jan. 20:
"Social Wasps," 1 to 4 p.m., featuring UC Davis distinguished professor Lynn Kimsey, director of the Bohart Museum. She recently received the 2023 Exceptional Faculty Award from the College of Agricultural and Environmental Sciences. Kimsey, a recognized authority on insect biodiversity, systematics and biogeography of parasitic wasps, urban entomology, civil forensic entomology, and arthropod-related industrial hygiene, is a 34-year member of the UC Davis entomology faculty. She has directed the Bohart Museum since 1990. She plans to retire in 2024. (See news story)
Saturday, Feb. 10:
13th Annual Biodiversity Museum Day, all day. Last year 13 UC Davis museums or collections participated: Arboretum and Public Garden, Bohart Museum of Entomology, Botanical Conservatory. California Raptor Center. Center for Plant Diversity, Department of Anthropology Museum, Marine Invertebrate Collection, Museum of Wildlife and Fish Biology, Nematode Collection, Department of Earth and Planetary Sciences Paleontology Collection, and Phaff Yeast Culture Collection.
"Grasshoppers, Crickets and Katydids." Talk and a question-and-answer forum from 1 to 2 p.m. Open museum, 2 to 4 p.m. Heading the event is UC Davis undergraduate student Sol Wantz, a senior majoring in entomology and a member o the lab of community ecologist and professor Neal Williams. She serve as president of the UC Davis Entomology Club.
110th UC Davis Picnic Day, all day. This is billed as the largest student-run event in the country. It is UC Davis' annual open house with hundreds of free and family friendly events. Entomology displays, exhibits and activities planned by the Department of Entomology and Nematology will be at the Bohart Museum and at Briggs Hall.
Sunday, May 19:
"Bees: Both Wild and Managed," 1 to 4 p.m. Presenters will include community ecologist Rachel Vannette, associate professor and vice chair of the UC Davis Department of Entomology and Nematology.
The Bohart Museum, founded in 1946, is located in Room 1124 of the Academic Surge Building, 455 Crocker Lane, UC Davis campus. It houses a global collection of eight million insect specimens, plus a live petting zoo (including Madagascar hissing cockroaches, stick insects, and tarantulas) and a insect-themed gift shop, stocked with t-shirts, hoodies, jewelry, books, posters, pens, and more.
The Bohart Museum is open to the public Monday through Thursday. Casual walk-in hours are from 9 a.m. to noon and from 1 to 5 p.m. Pre-arranged tours (schools, scouts, UC classes) may also occur during these times. The museum will be closed for the winter holiday break, Dec. 23-Jan. 1. More information is on the website or by contacting bmuseum@ucdavis.edu. Tabatha Yang serves as the education and outreach coordinator, and Brennen Dyer as the collections manager.
- 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.