Meeting Abstract

S8.1-2  Monday, Jan. 6 08:30  The role of pre-existing plasticity in adaptive evolution SERRATO-CAPUCHINA, G.A.; PFENNIG, D.W.*; Univ. of North Carolina, Chapel Hill; Univ. of North Carolina, Chapel Hill dpfennig@unc.edu

In order for adaptive evolution to occur, phenotypic variation must be present on which selection can act. Yet, relatively little is known about the source(s) of phenotypic variation or whether different sources affect adaptive evolution’s tempo and mode. Here, we review cases studies of natural populations to infer whether adaptive evolution came about strictly through genetically canalized change (i.e., change that reflects allelic or genotype frequency changes and that is relatively insensitive to the environment) or whether, alternatively, it may have arisen through phenotypic plasticity. Although the former is generally presumed to be the sole mediator of adaptive evolution, increasing evidence suggests that plasticity can promote adaptive evolution under certain circumstances, such as when reaction norms become a target of selection. We also consider how these two mechanisms can impact adaptive evolution’s speed. As we describe, phenotypic plasticity can promote rapid evolution, thereby increasing the chances that a population will adapt to changing environmental circumstances and persist. Finally, we consider how these two proximate mechanisms interact and affect adaptive evolution’s mode. In particular, because environmentally contingent phenotypes can lose their plasticity over evolutionary time, new traits that initially arise through phenotypic plasticity may eventually become genetically canalized. Indeed, adaptive evolution may proceed through an initial phase in which new traits are environmentally induced to a later phase in which these traits are expressed constitutively. In our review, we draw on cases studies of the proximate causes and evolutionary consequences of phenotypic plasticity, especially in the context of competitor- and predator-mediated selection, where rapid responses are often vital.