Research

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I conduct research at the interface of ecology, evolution, and development to understand why organisms vary in their responses to environmental changes, such as stress exposures and shifts in dietary resource availability. My empirical work typically integrates measures of whole organism performance with underlying molecular mechanisms, including physiology and gene expression. 

 

I am exploring this broad question in three related research themes, outlined below: 

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For decades, the field of life history evolution has aimed to understand why organisms vary in major fitness-related traits, such as reproductive investment and longevity. Only recently, however, have biologists started integrating proximate and ultimate approaches to understand how developmental processes shape the life history variation that is visible to selection. Using butterfly and amphibian systems, I combine measures of whole-organism performance (e.g., growth rate, reproductive effort, and lifespan) with physiology (e.g., oxidative stress, hormone levels, telomere length) to understand how the developmental environment influences variation in life history traits and the tradeoffs among them. 

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Representative publications: 

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Shephard et al. (2023) Metabolic stress as a driver of life-history plasticity: flight promotes longevity and antioxidant production in monarch butterflies. Proceedings of the Royal Society B. 

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Phenotypic plasticity provides a means by which populations can rapidly respond to novel environments over developmental time. Yet, we lack understanding of the mechanisms of plasticity that may allow populations to gain an initial foothold in novel or stressful environments, as well as why such mechanisms vary across individuals or populations. Using butterflies, I am integrating evolutionary and ecotoxicological approaches to test a role for generalized stress response pathways in facilitating tolerance to anthropogenic stressors, such as heavy metal pollution and changes in nutrient availability. Additionally, I use amphibian larvae to test the role of physiological stress responses in evolutionary transitions to novel diet types. 

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Representative publications: 

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Shephard et al. (2023) Anthropogenic sodium influences butterfly responses to nitrogen-enriched resources: implications for the nitrogen limitation hypothesis. Oecologia. 

 

Shephard et al. (2022) Anthropogenic zinc exposure increases mortality and antioxidant gene expression in monarch butterflies with low access to dietary macronutrients. Environmental Toxicology and Chemistry. 

 

Shephard et al. (2021) Evaluating costs of heavy metal tolerance in a widely distributed, invasive butterfly. Evolutionary Applications.

 

 

 

 

 

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The early life environment can have a significant influence on phenotypic development. Such "carryover effects" may therefore have consequences for both individual health and evolutionary or demographic processes. I study how early life stressors, such as dietary restriction and anthropogenic pollution, "reprogram" phenotypic outcomes at later life stages using both insects (e.g., crickets and butterflies) and amphibians. 

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Representative publications: 

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Shephard et al. (2024) Corticosterone contributes to diet-induced reprogramming of post-metamorphic behavior in spadefoot toads. Integrative Organismal Biology. 

 

Shephard et al. (2024) Early life nutrient restriction affects hypothalamaic-pituitary-interrenal gene expression in a diet type-specific manner. General and Comparative Endocrinology. 

 

Shephard et al. (2018) Hormetic effects of juvenile radiation exposure on adult reproduction and offspring performance in the cricket (Acheta domesticus). Dose-Response.  

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