My research broadly focuses on how variation in the environment facilitates the maintenance of genetic variation within and among populations. Current efforts examine thermal stress tolerance, expression of heat shock proteins, and how variation in these traits impact the evolution of life history traits. All organisms respond to high temperatures in part by activating several related gene families, known as stress or heat-shock genes. Their protein products are highly conserved structurally, and they function similarly in all organisms, whether bacteria, humans or Drosophila. In my laboratory, students have the opportunity to study the function and developmental regulation of these genes and examine how their evolution is constrained by their varied functions. Thus research will stretch from variation in DNA sequence to growth and fitness differences of individuals that express these genes at different levels - ideally with travels to Mexico.
A second project is a study of variation in the freshwater mussels present in the Cuyahoga watershed. More than a dozen species of Unionid mussels, one of the most threatened groups of organisms in the United States, occur within 800 sq. mi. region. To date, mussels have been found only within the Cuyahoga River and its largest tributary, Tinkers Creek. Because the Cuyahoga achieved infamy as one of the most polluted rivers in America in the early 1970s, its recovery, and that of the organisms within it may set an example for the potential to clean habitat once destroyed by overuse. We hope to track the recovery of mussels to the lower parts of this river. To follow long term change, I am investigating variation in species composition and isolation of populations present in the two rivers. Initial results for one species, using the 16s rRNA gene of mitochondria, suggest that populations in Tinkers Creek are isolated from those in the Cuyahoga. Increased resolution of genetic analysis may come from an exploration of variation in male-derived mitochondria. Biparental inheritance of mitochondria may be a feature unique to mussels, and one with unexplored potential to address population variation and concurrent evolution of the same gene expressed in different tissues.
Krebs, R. A., M. E. Feder and J. Lee. 1998. Heritability of expression of the 70kd heat-shock protein in Drosophila melanogaster and its relevance to the evolution of thermotolerance. Evolution 52: 841-847.
Krebs, R. A. and M. E. Feder. 1998. Hsp70 and larval thermotolerance in Drosophila melanogaster: How much is enough and when is more too much? Journal of Insect Physiology 44: 1091-1101.
Krebs, R. A. and V. Loeschcke. 1999. A genetic analysis of the relationship between life-history variation and heat-shock tolerance in Drosophila buzzatii. Heredity 83: 46-53.
Krebs, R. A. 1999.A comparison of Hsp70 expression and thermotolerance in adults and larvae of three Drosophila species. Cell Stress & Chaperones 4: 243-249.
Krebs, R.A. and Bettencourt, B.R. 1999. The evolution of thermotolerance and variation in the heat shock protein, Hsp 70. American Zoologist 39:910-919.
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CSU Department of Biological, Geological, and Environmental Sciences
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Update: 18 August, 2003