Figure 1.

Examples of Genotype‐by‐environment interaction and its absence. Nonlinear reaction norms for hypothetical genotypes 1, 2, 3, 4, and 5. In panel a, the reaction norms of genotypes 1 and 2 do not cross but are not parallel over a range of environments: G × E. In panel b, the reaction norms of genotypes 1 and 3 are parallel over the entire range of environments studied: no G × E. In panel c, the reaction norms of genotypes 1 and 4 are not parallel over a range of environments, and cross: G × E. In panel d, reaction norms of genotypes 1 and 5 are similar and parallel across “typical” environments for their population, but diverge dramatically in evolutionarily novel environments, illustrating cryptic genetic variation