3157 Genome Science Bldg, CB #3280
I have taken an experimental approach to the study of evolution because it allows me to address questions from many areas of evolutionary biology. Evolution experiments using microorganisms have been able to address widely ranging topics from kin selection and the evolution of virulence to the evolution of mutation rates, and the evolution of habitat (or host) specialization.
Although I am interested in all aspects of evolutionary biology, and students and postdocs in my lab are encouraged to develop independent projects that follow their own interests, the primary focus of my work has been to investigate the genetics of adaptation. I am using laboratory evolution experiments of bacteriophage (bacterial viruses) to address the following questions:
- Does adaptation occur by large or small steps?
- Are certain genotypes better able to adapt than others?
- Can we identify factors that shape the nature of interactions between mutations?
Bacteriophage serve as particularly suitable systems for addressing the genetics of adaptation because they offer the opportunity to observe events on an evolutionary timescale within weeks or even days. For example, we can watch evolution of the bacteriophage phi-6 in action. The following pictures were taken at different timepoints during the evolution of a low fitness phage genotype toward an adaptive optimum What you're seeing is a pale gray background that is the bacterial lawn and dark circles where phage have landed, replicated, and killed bacteria to make cleared circles that we call plaques. It is easy to monitor adaptation in phi6 because plaque size is a strong correlate of fitness (i.e. relative growth rate). As beneficial mutations appear and become common in adapting populations, fitness improves and plaque size increases.
Lohaus R, Burch CL, Azevedo RB (2010). Genetic architecture and the evolution of sex. J Hered. 101 Suppl 1:S142-57.
Knies JL, Kingsolver JG, Burch CL (2009). Hotter is better and broader: thermal sensitivity of fitness in a population of bacteriophages. Am Nat. 173(4):419-30.
Knies JL, Dang KK, Vision TJ, Hoffman NG, Swanstrom R, Burch CL (2008). Compensatory evolution in RNA secondary structures increases substitution rate variation among sites. Mol Biol Evol. 25(8):1778-87.
Guyader S, Burch CL (2008). Optimal foraging predicts the ecology but not the evolution of host specialization in bacteriophages. PLoS One. 3(4):e1946
Ferris MT, Joyce P, Burch CL (2007). High frequency of mutations that expand the host range of an RNA virus. Genetics. 176(2):1013-22.
Knies JL, Izem R, Supler KL, Kingsolver JG, Burch CL (2006). The genetic basis of thermal reaction norm evolution in lab and natural phage populations. PLoS Biol. 4(7):e201.
Azevedo RB, Lohaus R, Srinivasan S, Dang KK, Burch CL (2006). Sexual reproduction selects for robustness and negative epistasis in artificial gene networks. Nature. 440(7080):87-90.
Duffy S, Turner PE, Burch CL (2006). Pleiotropic costs of niche expansion in the RNA bacteriophage phi 6. Genetics. 172(2):751-7.