- Author: Kathy Keatley Garvey
Unlike honey bees, carpenter bees do not live in hives, they have no queen and they do not produce honey.
The work, published in the journal Molecular Ecology, focused on two species of carpenter bees, the Valley carpenter bee or Xylocopa sonorina, and the mountain carpenter bee, Xylocopa tabaniformis, from multiple geographic sites in their range, said corresponding author and community ecologist Rachel Vannette, an associate professor in the UC Davis Department of Entomology and Nematology.
The research suggests that “sociality may not be the main driver of microbiome structure in bees as is often assumed,” Vannette said.
Co-first author Madeline Handy, an undergraduate student and research intern in the Vannette laboratory and a member of the Research Scholars Program in Insect Biology (RSPIB), originated the research. Co-first author and microbiologist Dino Sbardellati of the Vannette lab and a graduate student in the UC Davis Microbiology Graduate Group, contributed bioinformatics and statistical analysis.
The researchers sequenced the microbial communities “using technology that produces longer reads from microbial DNA and allows us to get a better picture of the microbes that are found in the crop and gut, as well as their relatedness to each other,” Vannette said.
The significance of the research? “Social bees have a gut microbiome that's a model for human gut microbiomes—microbes contribute to digestion in the gut, affect host immunity and physiology in both bees and humans,” Vannette said. “But a key question is how do these types of microbiomes form and what maintains them? Social interactions has been posed as a major driver but this study suggests that advanced sociality is not required for the maintenance of this type of microbiome. Second, we show that long-read amplicon sequencing can be used in novel ways to generate hypotheses about how microbes are transmitted and maintained within insects.”
Next Steps. The next steps? “We would love to know what are these bacteria doing and if they are beneficial to bees. Our lab is excited to explore how bacterial and fungal communities in bee GI tract, stored food and other insect life stages like larvae or pupae may contribute to bee nutrition and health.”
The six-member team also included co-authors Michael Yu, UCLA Department of Ecology and Evolutionary Biology; Nicholas Saleh, Department of Entomology and Nematology Fort Lauderdale Research and Education Center, University of Florida, Davie; and Madeleine M. Ostwald, School of Life Sciences, Arizona State University, Tempe.
Their paper is titled “Incipiently Social Carpenter Bees (Xylocopa) Host Distinctive Gut Bacterial Communities and Display Geographical Structure as Revealed by Full-Length PacBio 16S rRNA Sequencing.”
Abstract:
“The gut microbiota of bees affects nutrition, immunity and host fitness, yet the roles of diet, sociality and geographical variation in determining microbiome structure, including variant-level diversity and relatedness, remain poorly understood. Here, we use full-length 16S rRNA amplicon sequencing to compare the crop and gut microbiomes of two incipiently social carpenter bee species, Xylocopa sonorina and Xylocopa tabaniformis, from multiple geographical sites within each species' range. We found that Xylocopa species share a set of core taxa consisting of Bombilactobacillus, Bombiscardovia and Lactobacillus, found in >95% of all individual bees sampled, and Gilliamella and Apibacter were also detected in the gut of both species with high frequency. The crop bacterial community of X. sonorina comprised nearly entirely Apilactobacillus with occasionally abundant nectar bacteria. Despite sharing core taxa, Xylocopa species' microbiomes were distinguished by multiple bacterial lineages, including species-specific variants of core taxa. The use of long-read amplicons revealed otherwise cryptic species and population-level differentiation in core microbiome members, which was masked when a shorter fragment of the 16S rRNA (V4) was considered. Of the core taxa, Bombilactobacillus and Bombiscardovia exhibited differentiation in amplicon sequence variants among bee populations, but this was lacking in Lactobacillus, suggesting that some bacterial genera in the gut may be structured by different processes. We conclude that these Xylocopa species host a distinctive microbiome, similar to that of previously characterized social corbiculate apids, which suggests that further investigation to understand the evolution of the bee microbiome and its drivers is warranted.”
Handy, who is pursuing her master's degree in public health, says her interest is “in all things microbiome, but I'm particularly interested in women's health and nutrition when it comes to the microbes living in our bodies.”
Sbardellati is interested in understanding how microbial ecology shapes macroscale ecology. In the Vannette lab, he studies bacteriophage (viruses which target bacteria) communities associated with the bumble bee gut and how phages shape gut microbial communities.
The Vannette lab is a team of entomologists, microbiologists, chemical ecologists, and community ecologists trying to understand how microbial communities affect plants and insects, and sometimes other organisms as well.
- Author: Kathy Keatley Garvey
When a Davis resident felled a plum tree, hordes of green-eyed, apricot-colored insects tumbled from the wood.
What were they?
They buzzed like bees. They loomed larger than bumble bees. And they disliked being disturbed.
The Davis resident took them to the Bohart Museum of Entomology, University of California, Davis, for identification.
“Male carpenter bees, Xylocopa varipuncta, also known as Valley carpenter bees,” said entomologist Lynn Kimsey, director of the Bohart Museum of Entomology and professor and chair of the UC Davis Department of Entomology.
“Some of us refer to these males as ‘teddy bear' bees, because of their yellowish-brownish color and fuzzy burly bodies,” said UC Davis emeritus entomology professor Robbin Thorp, who studies pollinators. “The females are all black with violaceous (violet) reflections on their dark wings.”
All females in the plum tree holes escaped.
Carpenter bees, so named for their ability to tunnel through wood to make their nests, carve with their mandibles (jaws) but do not ingest the wood. Only the females excavate the tunnels, which average six to 10 inches in depth.
Carpenter bees, measuring about an inch long, are the largest bees in California. Their eggs are the largest of all insect eggs. The Valley carpenter bee egg can be 15mm long.
The males are territorial, Kimsey said, and can be quite aggressive. They hover and lie in wait for passing females.
“We have them around our home (in Davis) when the wisteria blooms,” she said. “Many people think they're bumble bees because of their size. They think they're fluffy yellow bumble bees.”
Thorp said he tries to convince people to learn to live with these bees as “they are important pollinators in our environment and have potential as pollinators of some crops.”
“Carpenter bees are beneficial in that they pollinate flowers in native 
“These bees are not currently managed for crop pollination,” Thorp said, “but there have been some recent studies of their potential for pollination of greenhouse tomatoes. They are good at buzz pollination and can be managed by providing suitable nest materials.”
Due to their large size, carpenter bees cannot enter tubelike blossoms such as sage, so they slit the base of corolla, a practice known as “stealing the nectar” (without pollinating the flower).
The Valley carpenter bee species is commonly found in southern California but is not all that well known in the Central Valley. “I have observed them in the field in southern California and in the Sacramento area,” Thorp said. “In the past few years, they seem to have become more common in the Davis area. I even found a dead male on my driveway (in Davis) a month or so ago.”
Carpenter bees, especially the most common species in the Central Valley, X. tabaniformis orpifex, are often mistaken for bumble bees. Like bumble bees, female carpenter bees exhibit similar size and coloration. However, a carpenter bee generally has a hairless, shiny abdomen while the bumble bee abdomen is typically covered with dense hair, and often with yellow markings.
Thorp said three species occur in California. “Of the three species, X. varipuncta (with the golden teddy bear males) and X. tabaniformis orpifex are the only two that occur in the Central Valley,” he said. “The third species, X. californica occurs primarily in the foothill areas surrounding the Central Valley.”
To build their nests, the females select telephone poles, fences, decks, railings, eaves, siding, outdoor furniture and tree trunks. They prefer bare, unpainted or weathered wood, especially redwood, cedar, cypress and pine. They generally avoid painted or pressure-treated wood.
Carpenter bees overwinter as adults in the tunnels and emerge in the spring.
Brian Turner, the Bohart Museum 's public outreach coordinator, said the sculpted holes in the chunk of plum wood that the Davis resident brought in “look professionally drilled.” The holes are elongated and intricately sculpted to contain the brood and food storage.
Turner released the male carpenter bees, but museum visitors can see the plum wood holes.
The museum, located in 1124 Academic Surge, is dedicated to teaching, research and service. It houses the seventh largest insect collection in North America. The global collection totals more than seven million specimens, and focuses on terrestrial and fresh water invertebrates.
The museum is also home of the California Insect Survey, a storehouse of the insect biodiversity of California's deserts, ountains, coast and great central valley.
