Dmitri Petrov
Stanford University
Population Genomics of Rapid Adaptation
[When and where]
Organisms can often adapt surprisingly quickly to evolutionary challenges, such as the application of pesticides or antibiotics, suggesting an abundant supply of adaptive genetic variation. In these situations, adaptation should commonly produce ‘soft’ selective sweeps, where multiple adaptive alleles sweep through the population at the same time, either because the alleles were already present as standing genetic variation or arose independently by recurrent de novo mutations. In my talk I will argue that adaptation by soft selective sweeps should be the rule in all organisms with large census sizes and will oultine our approaches for quantification of adaptation by soft sweeps using population genomic data and experimental evolution. First, I will describe application of new statistical approaches to Drosophila genomic data that allowed us to discover that most recent and strong adaptation in Drosophila was driven by soft sweeps. I will argue that this is because population sizes relevant to adaptation in Drosophila are orders of magnitude larger than previously thought, profoundly changing the expected dynamics of adaptation. In the second part, I will describe how we quantify the dynamics of adaptation in large experimental populations of yeast using ultra-diverse barcoding system. We use this system to detect adaptive lineages and study their dynamics while they are still extremely rare and to follow them until they start interfering with one another. We use this approach to quantify the rate of adaptive mutagenesis and the distribution of selective effects of the mutations that drive the adaptive dynamics, as well as to determine the precise molecular identity of hundreds of individual adaptive mutations in a single experiment. I will discuss the implications of these findings for the search of signal of adaptation in the genome and for the possibility of predicting the path of adaptation in large populations.
Invited talk Mini-symposium 10
Updated May 18, 2015, by Minus