Research
Mutualistic interactions between species are vital to life. Organisms across all domains of life depend on other species for an array of important functions, including supplementing nutrition, providing defense against pathogens, and increasing tolerance to environmental stressors. Our lab investigates the coevolutionary dynamics that underpin long-term persistence of these mutualistic interactions. Our approach uses evolutionary genetics, empirical manipulation, analysis of natural populations, and experimental evolution. Our empirical work is guided by the foundation established by theoretical models. Our current work focuses on 1) leveraging molecular genomics techniques to identify the genetic basis of benefit exchange in a natural system of host and symbiont, 2) examining the evolutionary mechanisms underpinning symbiotic specialization versus generalism, and 3) assessing the eco-evolutionary costs of symbiosis. We conduct this work using the naturally occurring interactions between Coreid insects and their bacterial symbionts and a model system of mutualistic crossfeeding Saccharomyces cerevisiae.
Stoy Lab Research Overview
Our lab aims to advance understanding of the evolutionary genetics and coevolutionary dynamics underlying mutualism stability. We use natural systems, including interactions between Coreid insects and bacterial Caballeronia symbionts. We also leverage experimental evolution and synthetic biology using Saccharomyces ceresivisae. Using this multi-faceted approach, we address oustanding questions in the field of mutualism, such as....
What mechanisms facilitate long-term cooperation in horizontally transmitted symbiotic mutualisms?
How does generalist symbiosis evolve? How does generalist symbiosis persist?
How do generalism and environmental transmission shape the evolution and adaptation of microbial symbionts?
How do community-level dynamics alter pairwise evolutionary trajectories?
Current Research Areas
Identifying the genomic basis of symbiosis in Coreid-bacteria symbioses
Squash bugs and their symbionts
Insects in the family Coreidae depend on bacterial Caballeronia spp. symbionts. These insects require Caballeronia for both survival and development. My lab is currently leveraging molecular genomics techniques, including transposon mutagenesis, to identify essential symbiont genes required for symbionts to colonize hosts and provide fitness benefits. Using this approach, we aim to examine whether the genomic basis of symbiotic association is conserved across the various host species with which Caballeronia is associated. This work contributes to our larger goal of evaluating the mechanisms that catalyze and constrain evolutionary specialization in symbiotic associations. Using this approach, we also aim to develop strategies for symbiont-mediated pest management.
Species-rich interactions and generalism
Examining the temporal and spatial connectivity of symbiotic associations (Coreids and their symbionts)
Prior work testing patterns of Caballeronia specialization to their Coreid insect hosts has identified no obvious patterns of local adaptation (e.g. geographically structured specialization) or host-species specificity. Our prior population genomics approach leveraged 16s sequencing to characterize symbiont population structure. We are currently enhancing this approach by leveraging metagenomics and network-based analysis to test for spatial and temporal structure across symbiont populations associated with closely related host species. Our genomics approach is complemented by lab-based analysis examining whether within-host symbiont strain variation and temporal changes to this strain variation alters insect fitness. In the future, we will also aim to leverage metagenomic barcoding to examine how demographic stochasticity alters symbiont community structure across successive stages of symbiont transmission and acquisition.
Symbiont-mediated pest management
Squash bugs and Caballeronia
Squash bugs are agricultural pests, causing mechanical damage to cucurbit crops and vectoring the pathogen Serratia ureilytica (formerly Serratia marcescens), which causes cucurbit yellow vine disease (CYVD). The symbiont Caballeronia competitively excludes Serratia from squash bug guts, reducing their vector competence. In our current work, we are characterizing strain-level variation and identifying symbiont loci required for insect association. This has the potential to inform the development of symbiont-mediated pest control strategies in agricultural settings.
Strategies to alleviate pest burden are critical for both traditional and organic farmers. Insects evolving resistance to insecticides is a constant struggle for traditional farmers, and organic farmers are often left essentially defenseless. Farmers regularly experience devastating crop loss due to insect pests, which are estimated to reduce annual world-wide crop yields by 20-40%, resulting in more than $220 billion in economic losses. The US government alone is expected to pay farmers $42.4 billion to cover crop losses in 2025. Our research is uniquely suited to contribute solutions to agricultural challenges resulting from pest burden,
Generalism and Mutualistic Benefits
Saccharomyces cerevisiae
Specialization is expected to facilitate the evolution of mutualistic benefits because partners exert consistent selection on one another for a specific resource or service. However, mutualism is most often generalist with species interacting with multiple partners across space or time. The consequences of this variation for the evolution of mutualistic benefits is not well understood. Leveraging a synthetic model system of mutualistical yeast obligately dependent on one another for amino acid cross-feeding and experimental evolution, we are assessing how partner fidelity alters the evolution of mutualistic benefits, resource production, and resource use efficiency.
