Phenotypic plasticity

Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment.^[1][2] Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompasses all types of environmentally induced changes (e.g. morphological, physiological, behavioural, phenological) that may or may not be permanent throughout an individual's lifespan.^[3]

The term was originally used to describe developmental effects on morphological characters, but is now more broadly used to describe all phenotypic responses to environmental change, such as acclimation (acclimatization), as well as learning.^[3] The special case when differences in environment induce discrete phenotypes is termed polyphenism.

Generally, phenotypic plasticity is more important for immobile organisms (e.g. plants) than mobile organisms (e.g. most animals), as mobile organisms can often move away from unfavourable environments.^[4] Nevertheless, mobile organisms also have at least some degree of plasticity in at least some aspects of the phenotype.^[2] One mobile organism with substantial phenotypic plasticity is Acyrthosiphon pisum of the aphid family, which exhibits the ability to interchange between asexual and sexual reproduction, as well as growing wings between generations when plants become too populated.^[5] Water fleas (Daphnia magna) have shown both phenotypic plasticity and the ability to genetically evolve to deal with the heat stress of warmer, urban pond waters.^[2]