Lee Altenberg (KLI, Austria) The Deep Connection between Mutational Robustness and Mutational Time Dynamics.
The production of genetic variation is essential for the evolutionary process, but inescapably much of this variation is deleterious, and depresses the average fitness of a population below its maximal value. Haldane (1937) found for some simple models that, counterintuitively, this depression in fitness — the genetic load — was independent of the selection coefficients, and determined instead by the mutation rate. Departures from Haldane’s principle were found in 1999 due to the evolution of mutational robustness on neutral networks of genotypes. The genetic load was found to be determined by the topology of the neutral network. No quantification of how the topology determines the genetic load has been forthcoming. Here, bounds are placed on the genetic load through the eigenvalues and eigenvectors of the mutation matrix. The treatment goes beyond neutral networks to arbitrary fitness landscapes and reversible mutation matrices. The mutational relaxation time for a perturbation of genotype frequencies has a direct relationship to the mutational robustness under the same perturbation of genotype fitnesses. By taking a general approach, the behavior of different kinds of mutation — point mutation, copy number change, epigenetic mutation, as well as non-genetic information transmission such as dispersal — can be compared all within a unified framework, and their levels of robustness characterized.