Abstracts (first author)
Landscape ruggedness reduces genomic parallelism in experimental populations of Pseudomonas
The repeatability of adaptive evolution depends on the ruggedness of the underlying adaptive landscape, how fitness varies as a function of phenotype or genotype. Rugged landscapes are thought to promote divergent adaptation, with genotypes evolving towards distinct genotypic and phenotypic solutions determined by the number of available fitness peaks. By contrast, genotypes evolving on a smooth landscape containing a single adaptive peak are expected to converge on a single genotypic and phenotypic solution. Here we evaluate the genomic consequences of adaptation on rugged and smooth landscapes by quantifying the degree of genic parallelism observed following adaptive evolution by genetically distinct starting genotypes of Pseudomonas fluorescens evolving on two single carbon substrates, xylose and glucose. Previous work showed that these substrates differ in the number of adaptive solutions available to these genotypes, with xylose being a relatively more rugged landscape than glucose. We find that, consistent with expectation, DNA sequence evolution is less parallel in a rugged, compared to a smooth landscape. Our results suggest that the ruggedness of the adaptive landscape has a strong influence on the pattern of genomic evolution.