ADAPTIVE PHENOTYPIC PLASTICITY - TARGET OR BY-PRODUCT OF SELECTION IN A VARIABLE ENVIRONMENT

Explores the logical implications of the idea that plasticity is a character in its own right, illustrating that this view is: 1) inconsistent with the action of either stabilizing or directional selection within environments; 2) misleading because of an ambiguity in the assertion that plasticity and trait means are independent; and 3) unnecessary for a description of reaction norm evolution because the proposed effects of separate genes for plasticity can be produced either by environment-specific gene expression or by allelic effects that vary across environments, both of which are already incorporated into current genetic models of reaction norm evolution. For ecologically important characters such as morphology, physiology, and most behaviors, phenotypic plasticity in most quantitative characters is a by-product of selection toward different phenotypic values in different segments of a variable environment. -from Author