We have two overarching goals:
- To discover fundamental principles of the ecology and evolution of host-microbe symbioses. We use bees as a model to understand how these interactions work, with potential relevance for our own microbiome.
- To better understand and protect wild bee biodiversity. Bees are ecologically critical yet vulnerable members of many terrestrial ecosystems, and are vital for the pollination of many crops.
To address these goals, we use gnotobiotic bee experiments, automated behavioral tracking, cultivation of bacteria and parasites, construction of synthetic bacterial communities, 16S rRNA gene sequencing, and metagenomic sequencing. We also conduct fieldwork in various places—from neotropical forests (Colombia, Southern Mexico) to urban environments (e.g., Chicago IL, Madison WI, Laguna Niguel CA) to montane, desert, and wetland habitats in the western US.
Ongoing research projects
Why do symbioses break down?
Honeybees, bumblebees, and stingless bees are thought to have acquired specialized gut bacterial symbionts tens of millions of years ago, which subsequently co-diversified (loosely, with occasional horizontal transmission) with their hosts. They are also known to have certain beneficial functions for bees. Therefore, it is a puzzle why they seem to be lost so readily. In a recent paper, we found that an entire genus of stingless bees has permanently lost two of the core symbionts. In another ongoing project on neotropical bumblebees, we are finding that the symbionts are readily lost and replaced on ecological time scales—a form of “dysbiosis” that is very widespread, as reviewed here. We are now studying ecological drivers of this microbiome shift in wild bumblebee populations, and are developing experimental methods to test its consequences for bee health. We are also further exploring gut microbiomes across the stingless bee phylogeny to study symbiont extinction and replacement at a macroevolutionary scale.
How does the gut microbiome affect behavior, and vice versa?
Like humans, bumblebees live in family groups and exhibit complex social structure and behaviors. Both humans and bumblebees also exchange gut microbes via close social interactions. Recent work on the “gut-brain axis” is demonstrating that gut microbes can modulate animal behavior; conversely, behavior influences the microbiome (e.g., by facilitating microbial transmission between individuals). Bumblebees are a useful system to study these feedbacks, because their microbiomes and their behavior can be experimentally manipulated in the lab. We are collaborating with Dr. James Crall, who developed automated behavioral tracking methods for bumblebees, to explore this and other links between host behavior and the microbiome. We are also taking gut-brain axis research out of the lab and into the field through a collaboration with Dr. Felicity Muth, an expert in bee cognition. We are currently exploring links between gut microbiome composition and cognitive traits in wild bumble bee populations.
Community ecology, codiversification, and coevolution of bee microbiomes
We are embarking on large-scale bee microbiome surveys to explore ecological and macroevolutionary processes that govern host-microbe interactions. We are also establishing experimental methods to test local adaptation of symbionts and host-symbiont coevolution. This work involves taxonomically and spatially broad microbiome profiling of solitary bee and wasp diversity, integration with plant-pollinator network data, genome-resolved metagenomic sequencing, physiological and metabolic assays of bee gut-derived bacterial cultures, and in vivo colonization experiments in gnotobiotic bumblebees.
Microbial solutions to help bee conservation
We are working on tools that could be used to aid bee science and conservation. For example, we are testing fecal sampling as a nondestructive method for sampling gut bacteria and parasites of wild bees (including threatened species). We are also exploring the potential for bumble bee probiotics. These would necessarily be administered to managed species (such as B. impatiens in the United States), but might also help wild populations via reduced parasite spillover. Some top goals here are to find the “best” probiotic bacterial strains in terms of sustaining bumble bee health, understand ecological processes that influence probiotic establishment and stability (e.g. priority effects, diversity-function relationships, coexistence), and evaluate the likelihood of probiotic transmission to wild bees.