polyphenism (environmental polymorphism) The occurrence within a species of distinct morphological types (morphs) in response to environmental cues. The morphs, which may overlap in space and/or time, are the result of particular signals in the animals' environment, such as nutrition, temperature, or daylength, that interact with the animals' genes and ‘switch’ development of the young from one ‘program’ to another. The resultant morphs are better adapted to their environmental conditions or to fulfil a certain role in a social group. Polyphenism occurring in successive generations exposed to seasonal changes in the environment is termed cyclomorphosis. Compare polymorphism.

polyphenism(polypheny) The occurrence within a population of phenotypic differences, commonly specializations, which lack a genetic basis.