Research Interests

RESEARCH--TEACHING--PUBLICATIONS--OUTREACH--CONTACT

Overview of Research Interests

I am broadly interested in how organisms cope with environmental variation.  In particular, I am interested in why organisms vary in adaptive phenotypic plasticity, the ability of a genotype to express phenotypes appropriate to the local environment, and the consequences of plasticity for understanding how a population will respond to novel or changing environmental conditions.  I address these questions in a variety of systems (e.g., beetles, butterflies, birds), integrating tools from evolution biology, behavioral ecology, neurobiology, and molecular biology.

A basic understanding of the evolution of plasticity is essential to predicting how organisms will cope with global climate change, the spread of invasive species, and alterations to habitat.  Understanding limits in the ability of organisms to adjust to a range of environments also has implications for understanding how pathogens respond to multiple environments (e.g., antibiotics), and how humans respond, at times inappropriately, to current environments (e.g., obesity in response to modern diets). 

A central thesis of my research is that understanding the developmental mechanism of plasticity is crucial to predicting the nature and extent of costs of plasticity.  My postdoctoral research and dissertation research investigate the costs of innate and trial-and-error mechanisms of plasticity, respectively.

Trial-and-Error Mechanisms of Plasticity: Costs of Learning in Butterflies

Many forms of plasticity (e.g., acquired immunity, many learned behaviors) develop through a trial-and-error process, where an individual samples alternate phenotypes, and, after some developmental period, adopts the phenotype with the highest performance in the local environment.  This sampling process should be very developmentally costly, in terms of time, energy and exposure, and may require investment in extra tissues (e.g., neural tissue).  My dissertation research, in collaboration with Dan Papaj, investigated the costs of trial-and-error learning in butterflies.  We measured the ability of full sibling families of butterflies to learn to locate a common (green-colored) and rare (red-colored) host.  Global costs of plasticity, such as brain size at emergence (studied with Wulfila Gronenberg) and delays in reproduction (studied with Goggy Davidowitz), were present, but relatively small.  Specific costs of plasticity, such as changes in reproductive allocation with experience, were also present, particularly in the environment in which butterflies were not innately-biased (red host).  Thus, trial-and-error mechanisms of plasticity are associated with high developmental costs (e.g., exploration, large brain size, delays in reproduction), but selection in common environments (e.g., green hosts) may have reduced global costs relative to costs specific to rare environments (e.g., red hosts).

Innate Mechanisms of Plasticity: Costs of Nutritional Polyphenism in Dung Beetles

“Innate mechanisms” of plasticity develop in response to one or two environmental cues (e.g., photoperiod, chemical cues), which signal a cascade of gene expression, resulting in one of several alternative phenotypes.  Because these alternative phenotypes are molded more by "trial-and-error" processes across generations (evolution) and less by those within generations (e.g., learning), the costs of innate mechanisms of plasticity will likely be fundamentally different from those of trial-and-error plasticity.  My postdoctoral research, in collaboration with Armin Moczek, is investigating the developmental genetic mechanisms, and their associated costs, underlying a nutritional polyphenism in dung beetles.  Dung beetles of the genus Onthophagus respond to the nutritional content of their larval dung ball: in general, males with access to large, dung balls emerge as large, horned adults that fight with other males over access to females; males that grow in small, or low quality dung balls emerge as small, hornless adults, and use sneaker tactics to access females.  I am studying patterns of gene expression that are specific to each alternative morph, and the consequences of such environment-specific expression for the subsequent evolution of plasticity.

Diverse Responses to Environmental Variation

I am broadly interested in mechanisms by which individuals and populations respond to environmental variation, in particular the role of behavior in mediating these responses.   

My research has also considered ways in which previous experience (and learning) in an area may influence subsequent performance and habitat choice.  Dan Papaj and I have investigated, in Battus philenor, how experience distinguishing host plants from the surrounding background may be advantageous in a new search task with a similar background.  In collaboration with Dan Cristol, I investigated the effects of prior residence in an area on subsequent social status and resource acquisition in a flock of wintering birds.  Prior residence, a form of philopatry, should increase the ability of an organism to cope with novel or changing environmental conditions because the long-term benefits of staying in an area should outweigh the short-term costs of learning to survive in that area. 

I am also interested in the ways in which ecological gradients (e.g., sexual selection, climate) may drive divergence in signaling systems and thus accelerate speciation in response to environmental variation.  For instance, work with Alex Badyaev documented how an elevational gradient in sexual selection was correlated with song structure in a diverse group of finches. 

I am broadly interested in the evolution of development and life history in response to selection on phenotypic plasticity.  Rebecca Young and I are currently testing the hypothesis that changes in the timing of developmental stages may have significant effects on the evolution of plasticity.  Thus, while my overall research program focuses on the costs and evolution of phenotypic plasticity, I am interested in a wide range of factors that affect how organisms respond to environmental variation.

Spatial environmental variation following forest fire

Temporal environmental variation across rainy and dry seasons

Pieris rapae shows genetic
variation in host learning

Horned and hornless morphs of Onthophagus nigriventris

Battus philenor

Scarlet Tanager singing

Canada Geese:
precocial developers

updated May 15, 2008
photos by E. Snell-Rood
except beetles: by A. Moczek