Developmental Constraint and Plasticity

How the workings of development both limit which forms can evolve and allow organisms to produce different forms in response to their environment.

Definition

Developmental constraint is a limitation on the phenotypic variation that development can generate, biasing or restricting the directions evolution can take; developmental plasticity is the ability of one genotype to produce different phenotypes in response to different environmental conditions during development.

Scope

This topic covers two complementary ways development shapes evolution: developmental constraints, which restrict the range of variants that development can produce, and developmental (phenotypic) plasticity, the capacity of a single genotype to generate different phenotypes depending on environmental conditions. It also touches on evolvability — how the organization of development affects the capacity to generate adaptive variation.

Core questions

• How does development limit the kinds of variation available to evolution?
• How can the same genotype produce different forms in different environments?
• How do constraint and plasticity together shape evolutionary outcomes?
• How does the structure of development affect the capacity to evolve?

Key concepts

• Developmental constraint
• Phenotypic (developmental) plasticity
• Reaction norm
• Polyphenism
• Evolvability

Key theories

Developmental bias on evolution

Because development can produce some variants more readily than others, it biases the variation available for selection, so the structure of developmental processes helps channel the directions and limits of morphological evolution.

Mechanisms

Developmental processes channel variation in two ways. Constraints arise when the architecture of development makes certain phenotypes difficult or impossible to produce — for example, because key processes are interdependent — so variation is biased toward some outcomes and away from others. Plasticity arises when developmental programs are responsive to the environment, allowing a single genotype to produce a range of phenotypes described by a reaction norm; in some species this yields discrete alternative forms (polyphenism) triggered by environmental cues. Together, constraint and plasticity influence which variants are available for natural selection and therefore shape evolvability, the capacity of lineages to generate adaptive change.

Clinical relevance

The interplay of developmental sensitivity to the environment and constraint is relevant to how environmental factors during development affect later traits, providing context for developmental origins of variation. This entry is educational and not clinical guidance.

History

Debates in the late twentieth century over how much development constrains and channels evolution, alongside growing study of environmentally responsive development, brought constraint and plasticity to the centre of evolutionary developmental biology.

Key figures

• Stephen Jay Gould
• Mary Jane West-Eberhard

Seminal works

• gilbert2016
• carroll2005

Frequently asked questions

What is a developmental constraint?

It is a limit imposed by how development works on the kinds of body forms that can be produced, which biases the variation available for evolution.

What is developmental plasticity?

It is the ability of the same genotype to develop into different forms depending on environmental conditions, such as temperature or diet, experienced during development.