Polyphenism

Definition

A form of phenotypic plasticity in which a single genotype produces two or more discrete, alternative phenotypes in response to specific environmental cues, such as temperature, photoperiod, nutrition, or population density. Unlike continuous plasticity, polyphenism yields distinct, non-overlapping morphs rather than a graded spectrum.

Etymology

From Greek poly- (many) + phainein (to show, appear), referring to the multiple visible forms arising from one genotype.

Example

In the butterfly Precis coenia (now Junonia coenia), seasonal polyphenism produces distinctly patterned spring and summer wing morphs triggered by larval rearing temperature and photoperiod; cooler, shorter-day conditions yield the darker, more heavily marked spring form, while warmer, longer-day conditions produce the paler summer form.

Synonyms

• environmental polymorphism
• discrete phenotypic plasticity

Related Terms

• phenotypic plasticity
• Polymorphism
• reaction norm
• phase polyphenism
• caste polyphenism
• morph determination
• genotype-environment interaction

Usage Notes

Distinguished from genetic polymorphism, where multiple phenotypes arise from different alleles at one or more loci. Polyphenism is strictly environmental in origin, though the threshold for morph switching may itself be genetically variable. Common in insects with seasonal forms (wing pattern, color), phase polyphenism in locusts (solitary vs. gregarious phases), and caste determination in social Hymenoptera (queen vs. worker development mediated by larval nutrition). The term is sometimes restricted to cases with discrete alternatives, reserving 'phenotypic plasticity' for continuous variation, though usage varies.