Protein Evolution Under Multiple Opposing Selection Factors*

Models of evolutionary dynamics often focus on trajectories of variation due to a specific condition of selection, but the natural process often involves multiple, potentially opposing selection pressures. Understanding the strategies for variation in the context of complex selection pressures is critical for both basic and applied biomedical science. To better understand evolutionary dynamics under complex selection conditions, we will focus on three questions using a bacterial membrane protein as a model system:
(i) How are the constraints on multiple fitness conditions arranged in the protein sequence?
(ii) What is the extent and pattern of epistatic interactions between selection conditions?
(iii) What are the important epistatic interactions between mutations in protein sequence, how do they control the rate and mechanism of adaptation?

We will show how patterns of epistasis control the rate of adaptation, and will deduce the relationship between epistasis and evolutionary viability.