Ard Louis
University of Oxford
Evolutionary dynamics, the structure of genotype-phenotype maps, and the arrival of the frequent
[When and where]
Evolutionary dynamics arise from the interplay of mutations acting on genotypes and natural selection acting on phenotypes. How does the structure of the genotype-phenotype (GP) map affect evolutionary processes? By using models for RNA secondary structure, the HP model for protein tertiary structure and the polyomino model for protein quaternary structure[1], we investigate the following structural properties:
Correlations: Following on an early suggestion by John Maynard-Smith, we show that genotypes are strongly correlated, that is their mutational neighbours are be more likely to map to similar phenotypes than expected from random chance. Neutral correlations greatly enhance robustness above the threshold to allow large neutral networks. Non-neutral correlations lower the rate at which novel phenotypes are found by a population, but also lower the probability that a mutation leads to a deleterious phenotype. Thus correlations in GP maps enhance robustness, but have a more complex effect on evolvability.
Bias: Many GP maps show a strong bias: the vast majority of genotypes map to an exponentially small set of phenotypes. We develop a population-genetics model that takes the GP map bias into account. This allows us to calculate effects such as the arrival of the frequent, were phenotypes with many genotypes mapping to them can fix in a population even if their fitness is lower than other penotypes with fewer genotypes mapping to them [2]. Bias may also 1) help explain how evolutionary solutions are found in hyper-astronomically large genotype spaces, 2) provide a non-adaptive mechanism for homoplasy (convergence) and 3) be linked to the spontaneous emergence of modularity and symmetry.
[1] A tractable genotype-phenotype map for the self-assembly of protein quaternary structure, Sam F. Greenbury, Iain G. Johnston, Ard A. Louis, Sebastian E. Ahnert, J. R. Soc. Interface 11, 20140249 (2014) [2]The arrival of the frequent: how bias in genotype-phenotype maps can steer populations to local optima, Steffen Schaper and Ard A. Louis, PLoS ONE 9(2): e86635 (2014)
Invited talk Mini-symposium 9.
Updated May 12, 2015, by Minus