David Haak
Education
B.S. North Carolina State University 1997
M.S. North Carolina State University 2000
Ph.D. University of Washington, in progress
Evolution
Darwin recognized that many adaptations have arisin from the accumulation of many small mutations each playing a small role in the entire adaptive phenotype. But what about major leaps on the adaptive landscape as a result of small genes or even single alleles?
Adaptive radiation's in higher plants have been associated with genome duplication events and the production of secondary metabolites. While genome duplication events allow for course adaptation small genes of large effect in secondary metabolite production allow plants to "fine-tune" their response to their environment.
- Looking at toxic fruit allows a tight correlation with effects on fitness.
- Genes encoding secondary metabolite production are evolutionarily preserved.
- Insights into the evolution of biochemical pathways give us a window on the selection pressures that maintain them.
Chemical Ecology and Plant-Animal Interactions
Many of the most intricate and fundamental interactions between plants and their herbivores, pathogens, and pollinators are mediated by plant secondary metabolites – compounds with no known physiological (primary) function in the plants that produce them. Though it has long been recognized that many plants produce these metabolites in ripe fruit, their importance in mediating interactions between plants and seed dispersers, seed predators, and fruit pathogens remains largely unexplored. Given the tremendous influence of secondary metabolites on plant-herbivore interactions, consideration of their role in seed dispersal may be critical for developing general theories of dispersal ecology and plant-animal interactions.
Again using chilies as a model system the work here will entail studies on two chile species that are widely separated geographically and phylogenetically. One species occurs in Bolivia, a putative center of origin where 17 species in the genus overlap. The other occurs in southern Arizona, at the northern tip of the chile’s natural range. These species and field locations allow tests of the hypotheses at both the most ancestral ecological conditions (Bolivia) and most recently encountered habitats (Arizona), providing the opportunity to tease apart ecological fitting from adaptive function. Consumption of artificial fruits with and without capsaicin and of pungent and non-pungent (lacking capsaicin) chiles will be compared across an unusually wide diversity of frugivores (fungi, insects, vertebrates). The current view of fruit-frugivore interactions generally fails to acknowledge such a diverse array of frugivores and hence simplifies the complex selection pressures on fruits and secondary metabolites within those fruits.
Physiology and Biochemistry
When your only currency is carbon a fundamental dichotomy exists in allocation. What governs this biochemical tradeoff? Using molecular biology and fundamental physiological tools we are beginning to investigate ecological tradeoff's at a molecular level, where we can not only measure the cost but also make some predictions about the selection pressure maintiaing these tradeoffs.
Publications
In review:
Deutsch,C*. J. J. Tewksbury* R. B. Huey K. Sheldon C. Ghalambor D.C. Haak P. R. Martin. In review. Climate change will be most detrimental to tropical ectotherms. Nature submitted.
Tewksbury, J.J., Reagan, K.M, Caldaron, A.,Machnicki, N., Haak D.C., Levey, D.J.,In revision Evolutionary ecology of a major spice. Nature
Accepted:
Tewksbury, J.J., Levey, D.J., Huizinga, M., Haak, D.C., and Travaset, A. (2007) Ecology of a spice: Capsaicin in wild chilies mediates seed retention, dispersal, and germination. Ecology.
Freeman, S, O'Connor, E, Parks, J.W., Cunningham, M., Hurley, D., Haak, D.C., Dirks, C., Wenderoth, M.P. Prescribed Active Learning Increases Performance in Introductory Biology. CBE Life Sci Educ (2007) 6: 132-139
Tewksbury, J.J., Manchego, C., Haak D.C., Levey, D.J., Where did the chili get its spice? Biogeography of capsaicinoid production in ancestral wild chili species. Chemical Ecology (2006).
Levey, D.J., Izhaki, I., Tewksbury J.J.,Tsahar, E., and Haak, D.C. (2006) The primary importance of secondary compounds in fruits: case studies with capsaicin and emodin In: A. Dennis, R. Green, E. Schupp and D.Westcott, editors. Seed dispersal: Theory and its application in a changing world Wallingford, Oxfordshire, UK: CABI international.
Contact information
haakd@u.washington.edu(email)
David Haak
456 Kincaid Hall
Box 351800
Department of Biology
University of Washington
Seattle, WA 98195-1800
(O) 206-616-2132
(F) 206-616-2011
http://students.washington.edu/haakd
