R. Craig Stillwell

Department of Ecology & Evolutionary Biology
rcstill@email.arizona.edu
Phone: 520-626-8455
Mailing address: Biosciences West 310, University of Arizona, Tucson, Arizona 85721

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CURRENT RESEARCH

My research interests lie at the interface of evolutionary biology and ecology (evolutionary ecology). For my PhD, I studied the factors creating within-species variation in body size and sexual size dimorphism of two species of seed-feeding beetles, Stator limbatus and Callosobruchus maculatus. In particular, I examined how both temperature and diet created variation in body size and sexual dimorphism through phenotypic plasticity (environmentally induced changes to the phenotype). The results of my research consistently show substantial variation in sexual size dimorphism within-species mediated by differences in phenotypic plasticity of body size between the sexes.

Currently I am working with Dr. Goggy Davidowitz and Dr. Diana Wheeler studying the developmental basis of sexual size dimorphism using the tobacco hornworm, Manduca sexta, as a model system. In M. sexta, three major physiological factors determine adult size: growth rate, the timing of the termination of juvenile hormone secretion and the timing of ecdysone secretion leading to pupation (the interval to cessation of growth). Together these three factors explain 95% of the variation in body size. The goal of my research is to examine how these three factors influence sexual differences in the development of body size and how they change to produce variation in dimorphism with environmental conditions.