Phenotypic plasticity is ubiquitous and generally regarded as a key mechanism for enabling organisms to survive in the face of environmental change. Because no organism is infinitely or ideally plastic, theory suggests that there must be limits (for example, the lack of ability to produce an optimal trait) to the evolution of phenotypic plasticity, or that plasticity may have inherent significant costs. Yet numerous experimental studies have not detected widespread costs. Explicitly differentiating plasticity costs from phenotype costs, we re-evaluate fundamental questions of the limits to the evolution of plasticity and of generalists vs specialists. We advocate for the view that relaxed selection and variable selection intensities are likely more important constraints to the evolution of plasticity than the costs of plasticity. Some forms of plasticity, such as learning, may be inherently costly. In addition, we examine opportunities to offset costs of phenotypes through ontogeny, amelioration of phenotypic costs across environments, and the condition-dependent hypothesis. We propose avenues of further inquiry in the limits of plasticity using new and classic methods of ecological parameterization, phylogenetics and omics in the context of answering questions on the constraints of plasticity. Given plasticity's key role in coping with environmental change, approaches spanning the spectrum from applied to basic will greatly enrich our understanding of the evolution of plasticity and resolve our understanding of limits.
Bibliographical noteFunding Information:
This work was supported by the National Evolutionary Synthesis Center (NESCent), NSF #EF-0423641 for a working group (project leaders: CJM and CDS) and a short-term fellowship to CJM. Support from the National Science Foundation and other sources is gratefully acknowledged (CJM and HSC: NSF IOS-1052262, CJM: IOS-1146977; CDS: NSF DEB-1242294, DEB-1046328, OISE-0623341; JM: John Templeton Foundation and NIH RO1 GM076041 and GM104040; CKG: NSF DEB-0846175; RAR: NSF DEB 07-16149, DEB 11-19430; ESR NSF IOS-1354737). We thank scholars whose work in this area past and present has contributed to the vibrancy of this area of inquiry, and note the journal’s limits on the numbers of scholarly works that we were able to cite. Additionally we thank Allen Rodrigo (NESCent Director) and D Wilson and S Risbon at NESCent for their support for the working group. We further are grateful to the comments of Sam Scheiner, three anonymous reviewers and comments from the editors of this journal and special issue, which improved the manuscript.