Figure 2.

Diagram illustrating the synergy and complementarity hypotheses for the fitness benefit of having multiple plastic responses to an environmental change. Fitness is shown in the noninducing environment and inducing environment for two genotypes each with induced plasticity in a different trait (dotted and solid lines represent the two genotypes). Fitness is also shown for a genotype with plasticity in both traits (dashed line). (a) Synergy hypothesis: fitness in the inducing environment is greater when both plastic responses occur than for either response alone, shown by the greater fitness of the combined response (dashed line) than either individual response (solid or dotted). (b) Complementarity hypothesis: the fitness benefit of each plastic response is greater in a different inducing environment. Each plastic trait may be beneficial in all inducing environments, but trait one (solid line) provides a greater benefit in the first environment, while trait two (dotted line) provides a greater benefit in the second environment. An organism with plasticity in both traits (dashed line) can have high fitness in both environments even if no additional benefit is provided by expressing both traits simultaneously (i.e., no synergy).