Figure 2

The conflicting properties of robustness and evolvability and their proposed resolution. A system (central node) is exposed to changing conditions (peripheral nodes). Robustness of a function requires minimal variation in the function (panel a) while the discovery of new functions requires the testing of a large number of functional variants (panel b). The existence of a neutral network may allow for both requirements to be met (panel c). In the context of a fitness landscape, movement along edges of each graph would reflect changes in genotype while changes in color would reflect changes in phenotype.