Fig 1. Different numbers of sequence-coding units K result in different mutational structures of the fitness landscape.

Examples of two fitness landscapes with K = 2 and K = 4 and the same number of genotypes N = 16. Grey arrows show the direction of increasing fitness. Two accessible pathways (black = with indirect mutations, green = without indirect mutations) have been highlighted. For K = 4, indirect mutations can be either backward (increasing the Hamming distance from the target genotype) or distance-neutral (the Hamming distance remains unchanged).