The genotype-phenotype map of an evolving digital organism
Fig 2
Genotype space characterization.
(A) A measure of the fraction of viable genotype space (see Methods) in the neighborhood of 1000 merely viable genotypes. We computed the number of 1-mutant neighborhoods of merely viable organisms, in which a particular phenotype (including the merely viable) appeared at least once, divided by 1000, i.e., by the total number of neighborhoods examined. We then normalized this quantity so that the sum equals one. Few phenotypes (e.g., that of merely viable organisms and of organisms able to perform the NOT operation) are moderately frequent, whereas most others (e.g., the NOR phenotype) are rare. (B) Genotypic distances between 100 pairs of genotypes per phenotype, after random walks aiming to reach one genotype from the other through multiple phenotype-preserving point mutations. Distance was measured as the number of positions at which both genotypes differ (Hamming distance). (C) Classification of genotypes that lie in the 1-mutant neighborhood of every organism having a particular phenotype (x-axis). Each bar shows the fraction of those genotypes that are non-viable (light gray), viable having the same phenotype as the focal phenotype (dark gray), and viable but having a distinct phenotype (black). Phenotypes are arranged from left to right in order of increasing complexity. Panels B-C are focused on single-trait phenotypes (i.e., phenotypes whose organisms have only the functional trait posed by a single logic operation) as well as merely viable organisms (labeled as no-trait).