Phenotypic plasticity/norm of reaction in evolutionary theories: questions, challenges, formalizations

Natural selection operates on phenotypes. In contrast, Modern Synthesis (the most formalized evolutionary theory) is essentially gene-centered or, more generally, genotype-centered. The organism's phenotype is considered, at best, as an image of the underlying genotype by a fixed mapping. General biology, however, knows examples where the genotype-phenotype dependence (mainly via ontogenesis and behavior) is very nontrivial and depends on external factors. This is traditionally captured by the notions of phenotypic plasticity and norm of reaction. Their effect on the evolutionary process is currently poorly understood due to the lack of a concise formalization. In this talk I will review the history of the question starting from the work of Baldwin, the stabilizing selection of Schmalhausen, and the epigenetics/genetic assimilation of Waddington, and ending with the modern Evo-Devo, Extended Evolutionary Synthesis, and Epigenetic Theory of Evolution. Finally, I will make an overview of attempts on mathematical conceptualization and computational modeling of the subject. Some parallels with results on computational RNA folding will be discussed, too.