FIGURE B2.

Fitness‐phenotype relationships are not static and environmental change may cause a shift in the fitness function (panel a) setting the stage for NFDS. This fitness differential can drive a shift in phenotype (panel b) that ultimately increases the relative abundance of the new phenotypes (panel c). Initially, the response to directional selection results in an increase in fitness that increases the relative frequency of new phenotypes (Z′). However, as the new phenotypes (and genotypes) become more abundant they can deplete the resources they have recently adapted to exploit and directly create a change to their fitness function (panel d) initiating NFDS.