Speaker
Description
The adaptation of a population to a novel environment proceeds through the fixation of beneficial mutations and the purging of deleterious ones. Although most novel mutations are deleterious, in well-mixed populations their effects become largely negligible at large population size. By contrast, in structured populations deleterious mutations can dominate the behavior even in the limit of infinite size. In the first part of the talk I will explain this phenomenon in the context of Muller's ratchet in spatial habitats. I then move on to graph-structured populations undergoing either (stochastic) origin-fixation dynamics or (deterministic) mutation-selection dynamics. In both settings, we have identified classes of graph structures for which the effect of deleterious mutations persists or even dominates in large populations. Specifically, these are amplifiers of fixation (on which deleterious mutations fix with finite probability in the limit of infinite population size) and amplifiers of mutation (which display a nonzero mutational load at mutation-selection balance in the limit of vanishing mutation rate). The talk is based on joint work with Suman Das, Jakub Otwinowski, Su-Chan Park, Nikhil Sharma and Arne Traulsen.
