Mutation landscapes.

A traditional picture of evolutionary dynamics with constant fitness is that of genomes living in sequence space and adapting on fitness landscapes. Mutation rates are considered to be constant or externally regulated. If, however, we take into account that genomes also encode for enzymes that perform replication and error correction, then individual genomes not only have a specific replication rate (fitness), but also a specific mutation rate. This leads to the concept of a mutation landscape. We explore evolution on mutation landscapes. Localization in pure mutation landscapes is only possible under extremely restrictive conditions. Coupling of mutation landscapes and fitness landscapes leads to localization and hence adaptation and evolution. We analyse how mutation landscapes facilitate localization in fitness landscapes and vice versa. Finally, we show that for mutation landscapes, at equilibrium, with constant environment, there is not necessarily selection for the minimum mutation rate. Instead, the target of selection is an optimum distribution of mutation rates, a 'mutational quasispecies'.