Abstracts (first author)
Impact of gene architecture on the adaptation rate
The accumulation of spontaneous beneficial mutations is one of the drivers of survival and adaptation in novel environments. Predicting the fitness effects of mutations and explaining them from a functional point of view are among the major goals of modern evolutionary biology. The rate and effects of spontaneous beneficial mutations are expected to depend on the environment, on demography and on genotype. Different models have been proposed to predict and explain the effects of new mutations from the underlying phenotypes. Here we measure the adaptation rate of fission yeast strains with different genome architectures. These strains have identical gene composition. However, they vary in gene expression and show substantial variation for fitness. By following the course of evolution of neutral markers in populations of these strains, we are able to estimate the rate and distribution of effects of new mutations. We use a variant of Fisher's geometrical model (FGM) which can explain the data, while capturing the functional details of the system. FGM predicts that the adaptation rate is a function of initial fitness, even when these differences come from changes affecting multiple genes, as is the case with genomic rearrangements. Our results, taken together with recent observations in experimental evolution, point to the existence of a single peaked landscape with minute complexities at the microscopy level, but a smooth upward climb on the macroscopic level.