Adaptation (process): the process whereby a complementary match between organism and environment arises through interactions between natural selection and internally and externally expressed constructive development.
Constructive development: the developing organism shapes its own developmental trajectory by responding to environmental inputs and altering internal and external states.
Cryptic genetic variation: genetic variation that normally has little or no effect on phenotypic variation but is expressed under atypical conditions.
Developmental bias: the nonrandom generation of phenotypes by developmental systems, with variants sometimes being channeled or directed by the processes of development towards functional goals (see also facilitated variation). The term encompasses both active and passive developmental constraints.
Ecological inheritance: the accumulated environmental changes, and associated selection pressures, that previous generations have brought about through their niche-constructing activity, and which descendant organisms inherit.
Evolution: a transgenerational change in the distribution of heritable traits of a population.
Facilitated variation: viable or functional variation that is expressed due to highly conserved core components or processes that function in development and physiology.
Genetic accommodation: gene frequency change due to selection on variation in the regulation, form, or side effects of the novel trait in the subpopulation of individuals that express the trait.
Genetic assimilation: a form of ‘genetic accommodation’ that occurs when natural selection causes environmentally induced (i.e. plastic) phenotypes to lose their environmental sensitivity over evolutionary time.
Heredity: all causal mechanisms by which offspring come to resemble their parents.
Inclusive inheritance: parental transference of developmental resources (mediated through genetic, epigenetic, physiological, behavioural and ecological mechanisms) that enable reconstruction of life cycles.
Niche construction: the process whereby organisms transform environmental states, and thereby modify the selection pressures to which they, and other organisms, in current and subsequent generations, are exposed.
Phenotypic accommodation: the adaptive mutual adjustment during development of variable parts of an organism, without genetic change.
Plasticity-first evolution: a mechanism of adaptive evolution in which environmental induction leads to developmental reorganization and production of a novel developmental variant that is accommodated by individual phenotypes. If the environmental stimulus is recurrent, the phenotype will be refined and stabilized by genetic accommodation.
Polyphenism: environmentally induced alternative phenotypes.
Reciprocal causation: process A is a cause of process B and, subsequently, process B is a cause of process A. Reciprocal causation captures the idea that developing organisms are not solely products, but are also causes, of evolution.
Some definitions adapted from:
West-Eberhard MJ. Developmental plasticity and evolution. Oxford University Press; 2003.
Levis NA, Pfennig DW. Evaluating “Plasticity-First” Evolution in Nature: Key Criteria and Empirical Approaches. Trends Ecol Evol. 2016;31(7):563-574.