Stochastic Polyphenism: Coping with Uncertainty

Polyphenism (i.e., polymorphism in which non-genetic differences can cause the development of the contrasting forms) can be conditional or stochastic. In conditional polyphenism, a genotype responds to different current environments that predict different future environments by producing different, appropriate phenotypes. For example, short days may cause the development of the diapause phenotype, appropriate to winter, and long days may cause the development of the nondiapause phenotype, appropriate to summer. In stochastic polyphenism, a genotype responds to differences in its environment that occur with probabilities approximating the probabilities of different future environments. For example, if 30% of winters are severe enough to require diapause and the other 70% yield a corresponding advantage to nondiapausing morphs, a genotype would produce the diapause phenotype 30% of the time and the nondiapause phenotype the other 70%. Modeling and empirical evidence support the concept of stochastic polyphenism.