Fig. 1.

—Types of phenotypic variation. (A) Expected change in the mean and variance between environments for the different types of phenotypic variation. Black dots and error bars indicate a shaded environment; orange indicates full sunlight. Error bars represent the true variance, as if the whole population was sampled. (B) Frequency distributions of phenotypes in the two environments. (C) Illustration of the four types of phenotypic variation, using hypocotyl length as an example phenotype. (i) An invariant response to the presence of shade/sunlight, such as that shown by shade-avoiding species which exhibit little phenotypic plasticity in response to shading (Gommers et al., 2013). (ii) A plastic shade avoidance response where hypocotyl elongation is triggered upon perception of shading (Pierik and de Wit, 2014). (iii) A variable hypocotyl length phenotype that varies within each environment but is not affected by shading. (iv) A variable and plastic hypocotyl length phenotype, which varies both within and between environments.