Using artificial selection to understand plastic plant phenotypes

The plasticity of any given trait, which has a genetic basisand which may or may not be adaptive, can intensify or attenuateevolved responses, and can itself evolve in response to selectiondepending on the scale of spatial or temporal heterogeneity.To investigate the complex function and evolution of plastictraits, an appealing yet challenging approach is assessing responsesto artificial selection. Here, I review how artificial selectionhas been employed to explore four botanical research themes:(1) relationships between plastic and evolved responses to multiplestresses, (2) integration of cellular, leaf-level, and whole-plantresponses to altered CO₂ concentrations, (3) photomorphogenicand photoperiodic development, both mediated by phytochromephotoreceptors, and (4) the evolution of the pest-induced myrosinase-glucosinolatesystem in cruciferous plants. These diverse topics are unifiednot only because they have been studied using artificial selectionexperiments, but also because they have considered variabilityin multiple traits affected by multiple factors in the externalenvironment. Limitations of such research include a dearth oflong-term studies; a surprising but often logistically necessaryomission of control or replicate lines; and numerous issuesrelating to assessing impacts of inbreeding and drift. In additionto discussing options for circumventing such limitations, Idraw attention to strategies for integrating the results ofartificial selection studies with progress in functional andevolutionary genomics.