My research addresses fundamental questions about the evolution and ecology of parasite avoidance. As a host's first line of defense, avoidance reduces initial contact with parasites and pathogens. I aim to understand the causes and consequences of variation in parasite avoidance in nature. My approach combines evolutionary theory and lab experiments to examine questions motivated in part by (and finding ground truth in) my past behavioral ecology research.
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Motivated to address gaps about the evolution and mechanisms of avoidance, I now focus empirically on the nematode host Caenorhabditis elegans and bacterial parasite Serratia marcescens, taking advantage of the cellular and molecular toolkit that is available for probing form-function links in this highly tractable model organism. My theoretical work takes the form of population-genetics models that make broad predictions about conditions and processes governing avoidance evolution and maintenance of genetic diversity in avoidance. I aim for the empirical and theoretical arms of my research to inform and motivate one another.
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C. elegans nematodes crawl through a lawn of the red-pigmented pathogenic bacterium S. marcescens.
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The overarching objective of my research is to establish a rigorous, theoretically grounded framework for the study of parasite avoidance evolution and ecology. These are some of the central questions motivating my work:
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What is avoidance?
Defining avoidance as the pre-contact defense identifies that avoidance is the first in a cascade of sequential defenses a host can mount. Post-contact defenses, like resistance, are expected to matter more to host fitness if avoidance has failed. This definition also highlights that avoidance broadly encompasses not only behavioral traits, but also phenological or structural forms of avoidance. |
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How does avoidance evolve?
Most research on parasite avoidance assumes these traits are adaptations, i.e., they have evolved through natural selection. My research tests the basic assumptions underlying this intuition. Is there heritable variation in parasite avoidance in natural populations? What are the fitness benefits and costs of avoidance? |
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How does avoidance influence the evolution of other defenses, like resistance?
Avoidance and resistance are commonly hypothesized to trade off with one another, following the argument that hosts may need one or the other defense, but not both. I examine this hypothesis and the underlying assumptions about the interactions between avoidance and resistance. How do we expect avoidance and resistance to covary? Is there a genetic or mechanistic basis for their covariance? How does the sequence of the defenses influence their evolution? As the first defense, does avoidance have cascading effects on later defenses, potentially shielding them from selection? 
The 'defense cascade,' where avoidance is the first in a sequence of defenses that prevent sequential steps in the parasite infection process (from Amoroso et al. 2025 Curr Biol, figure made with BioRender.com)
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How do hosts balance the benefits and costs of avoidance in natural contexts?
My PhD research focused on parasite avoidance behavior in red-fronted brown lemurs (Eulemur rufifrons) in western Madagascar, examining how they selected among scarce water sources during the dry season. I found that lemurs preferred clean water that had less risk of parasite transmission, but these preferences were not always borne out in their choices, which were also influenced by factors like travel distance and predator risk. This research raised questions for me about how these behaviors evolved -- questions I found were well suited to theoretical and laboratory methods that I pursued in my postdoc. In the future, my research will sample from naturally co-occurring C. elegans and S. marcescens strains to consider my empirical work in an ecologically informed context. |
