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 simply by monitoring increases in plaque size . As beneficial mutations appear and become common in adapting populations, fitness improves and plaque size increases.