THE ADAPTIVE ADVANTAGE OF PHENOTYPIC MEMORY IN CHANGING ENVIRONMENTS

The adaptive value of carry-over effects, the persistence of induced p henotypes for several generations despite the change in the conditions that first induced these phenotypes, is studied in the framework of a simple model. Three different organismal strategies - non-inducible ( genetic), completely inducible (plastic), and intermediate (carry-over )-are compared in fitness terms within three different environments. A nalytical results and numerical simulations show that carry-over effec ts can have an advantage in stochastic environments even over organism s with high adaptive plasticity. We argue that carry-over effects repr esent an adaptive mechanism on the ecological timescale that fills the gap between short-term individual adaptations and long-term evolution ary adaptations. An extension of the concept of plasticity to incorpor ate the time dimension and include the stability of induced phenotypes through both clonal and sexual generations, is suggested.