The major goal of my research is to understand the evolution of conflict and cooperation, especially in systems that involve bacteria and/or mobile genetic elements. Much of my work uses quantitative experimental approaches, including experimental evolution. I also use mathematical modelling to address conceptual issues, derive testable predictions, and interpret empirical results.
Cooperation among microbes
An explosion of research in recent years has shown that many important microbial phenotypes—including traits involved in pathogenicity, metabolism, and development—are cooperative: they increase the fitness of other nearby cells or virions. What types of social interactions occur among microbes? What is the genetic basis of these interactions? What limits the spread of cheaters that benefit from a cooperative trait without paying the fitness cost of producing it?
Symbiosis and infectious disease
Symbioses are intimate associations between two species that can be good for both (“mutualism”) or good for one species but not the other (“parasitism”). Unlike cooperation within species, where kin selection provides a unifying evolutionary principle, there is no well-supported theory that explains symbiosis. When do symbioses evolve to be mutualistic and when do they evolve to be parasitic? When do infectious diseases (one kind of symbiosis) evolve to be more harmful or less harmful? Why are so many bacterial genes involved in symbiosis carried by mobile elements like plasmids and phage?