Ecology, Evolution, and Development: The Conceptual Foundations of Adaptive Phenotypic Plasticity in Evolutionary Ecology

Emerging Sciences of Adaptive Phenotypic Plasticity

During the early 1980s, a rapid expansion of research literature concerning what its authors called phenotypic plasticity began to take shape. The scientists that contributed to this literature -- largely within the broad field of evolutionary ecology -- asked questions like, “How is phenotypic plasticity adaptive?”, “What is its genetic basis?”, “How might it evolve?”, and “How might it impact the direction and dynamics of evolutionary change?” They investigated adaptations in a great diversity of organisms, drawing on and reinterpreting concepts that geneticists had long used to describe the effect of environments on organismal development, such as the norm of reaction and genotype-environment interaction (GxE). What biologists often considered to be merely a source of noise or uncertainty in genetical and evolutionary investigations became an important object of investigation as an evolutionary phenomenon.

My Driving Question: How did adaptive phenotypic plasticity become such an important object of investigation for evolutionary ecologists during this period?

The dominant mythology surrounding contemporary phenotypic plasticity research holds that empirical and theoretical investigations of plasticity in an evolutionary context were stifled by rampant "gene centrism" throughout the 20th century: researchers were too concerned (it is said) with demonstrating hereditary differences in organisms, and wrote off plasticity as simply an annoying source of experimental error. My dissertation offers a different perspective, by showing how the articulation of an evolutionary-ecological science of adaptive phenotypic plasticity in the 1960s through 1980s was contingent upon -- and intertwined with -- the emergence and conceptual evolution of what we now call evolutionary population ecology. Specifically, my dissertation focuses on the two-pronged hypothesis that the emergence of the contemporary science of adaptive phenotypic plasticity depended on two factors: (1) a dramatic change during the 1950s and '60s in how ecologists thought about the temporal and spatial scales of evolutionary change, and (2) the increasing use of phenotypically-oriented mathematical techniques (such as game theory and optimality modeling) that provided new languages for talking and reasoning about phenotypic evolution.

I use a combination of archival research, oral history interviews, and analysis of the published scientific literature to reconstruct key investigative pathways that produced unique and highly influential conceptual and theoretical approaches to investigating adaptive phenotypic plasticity. These reconstructions show not merely that decisions about the units of environmental change, organismal characteristics, and hereditary mechanisms are tightly linked in evolutionary-ecological models, but how scientists have navigated these issues in specific social, intellectual, and material contexts. I analyze how the specific contexts in which adaptive phenotypic plasticity was investigated during the 1960s through 1980s shaped assumptions and commitments hidden in the unique concepts and models that emerged from those investigations. This project informs ecological research and scientific policy-making by illustrating some consequences of those contingent assumptions and commitments for efforts to integrate evolutionary and ecological theory, using concrete cases from the history of science.

What is Adaptive Phenotypic Plasticity?

Ecologists are increasingly aware that models based on the assumption of an unchanging ecological “niche” into which a species “fits” are too simplistic, and are unlikely to produce accurate predictions about how species will respond to environmental change. The range of conditions in which a species can persist can be affected by changes both in a species' traits, and in the traits of individuals within a species. Such changes can result from rapid evolution in response to new environmental challenges, or from phenotypic plasticitythe ability of individual organisms to respond morphologically, physiologically, or behaviorally to changes in environment. In some cases, phenotypic plasticity can facilitate evolutionary change by allowing a species to persist in a sub-optimal environment long enough for new adaptations to arise. In addition, changes in climate can result not only in unidirectional shifts in environmental conditions, but also in changes in patterns of environmental variability, creating evolutionary pressures that can alter the way that organisms respond to environmental conditions. That is, adaptive phenotypic plasticity.

Efforts to make accurate predictions about how species will respond to environmental change depend on better understandings of interacting evolutionary, developmental, and ecological processes. In light of attempts to integrate models of adaptive phenotypic plasticity into ecological models of species distribution, it is crucial to understand how the specific social, intellectual, and material contexts in which models of plasticity emerged during the 1960s through 1980s shaped the hidden assumptions and commitments that they contain.

This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. 2011131209, and NSF SBE Doctoral Dissertation Research Improvement Grant No. 1256752.