Fig. 2

Cartoon of the mapping of a genotype space into phenotypes in two different environments. Each layer (E1, E2) represents an environment. In each of them, genotypes express different phenotypes with different fitness values. Red dashed arrows indicate possible cases of functional promiscuity: if the population contains a genotype in the region of the yellow phenotype (in E1) that overlaps the blue phenotype (in E2), the function required in E2 is performed, though with a decreased proficiency. For the sake of a clearer representation, not all possible transitions between phenotypes have been depicted