Mathematics Colloquium: Paul Joyce

Thursday, March 22 2012 at 3:30 PM

Location: TLC 032

Mathematics Colloquium with Paul Joyce, University of Idaho, titled "Mutational Effects and Population Dynamics during Viral Adaptation Challenge Current Models," will occur March 22 at 3:30 p.m. in TLC 032.

ABSTRACT: Adaptation by natural selection can follow a stepwise process. At each step of adaptation a mutation arises, the mutant has higher fitness than the wildtype, and the new mutations fixes in the population. In this talk we explore the distribution of first and second steps of adaption. For the viral data under review we show that the distribution of first-step adaptive mutations differed significantly from the distribution of second-steps, and a surprisingly large number of second-step beneficial mutations were observed on a highly fit first-step background. We will discuss two commonly used mutational landscape models: the uncorrelated (rugged) landscape model and the additive (smooth) landscape model. Collectively, the results of the viral adaptation experiments indicate that the fitness landscape falls between the extremes of smooth and fully uncorrelated, violating the assumptions of many current mutational landscape models. However, a third explanation based on Fisher¹s geometric model provides a better explanation of the data.

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