Figure 1. Canalization minimizes phenotypic variation.

A. Quantitative traits exhibit some degree of variation, represented here by a distribution. A canalized trait shows tight distributions (blue) regardless of genetic or environmental perturbation. Some traits can be de-canalized by environmental or genetic perturbations which increases the degree of phenotypic variation (green). B. A possible mechanism of assimilation of a new phenotype occurs via de-canalization. Over several generations of selection for a crossveinless wing phenotype in Drosophila, the rare phenotype was assimilated to a large fraction of the population.