Speaker: Dan Beller (Physics, faculty)
Title: Genetic lineage trees in populations undergoing range expansion
Abstract: When a biological population expands into new territory, genetic drift (chance variations in allele frequency) develops an enormous influence on evolution at the expansion front. In such range expansions, fluctuations in allele frequencies occur through stochastic spatial fluctuations of both genetic lineages and the boundaries between genetically segregated "sectors". However, we are only just beginning to understand the statistics of these fluctuations, and even less is known for range expansions in heterogeneous environments. This talk will focus on theoretical and numerical approaches to predicting patterns of relatedness in model microbial systems through the fluctuation statistics. I will introduce some variations on the "stepping-stone model" used to simulate spatially structured populations. I'll then overview some topics we've been studying in recent and current work: the genetic signatures of local catastrophes, topographic variation, spatially variable evolutionary selection, and mechanical "active nematic" interactions between cells.