Relationship among Phenotypic Plasticity, Genetic and Epigenetic Fluctuations, Robustness, and Evolovability; Waddington's Legacy revisited under the Spirit of Einstein

TL;DR

This paper establishes quantitative relationships among phenotypic plasticity, genetic and epigenetic fluctuations, robustness, and evolvability, supported by models and experiments, revisiting Waddington's legacy in evolution-development.

Contribution

It introduces an evolutionary stability framework to derive proportional relationships among plasticity, fluctuations, and evolvability, providing a quantitative basis for canalization and genetic assimilation.

Findings

Plasticity is proportional to environmental responsiveness.

Phenotypic fluctuations of genetic and developmental origins are quantitatively related.

Evolvability correlates with phenotypic variance and responsiveness.

Abstract

Questions on possible relationship between phenotypic plasticity and evolvability, as well as that between robustness and evolution have been addressed over decades in the field of evolution-development. By introducing an evolutionary stability assumption on the distribution of phenotype and genotype, we establish quantitative relationships on plasticity, phenotypic fluctuations, and evolvability. Derived are proportionality among plasticity as a responsiveness of phenotype against environmental change, variances of phenotype fluctuations of genetic and developmental origins, and evolution speed. Confirmation of the relationships is given by numerical experiments of a gene expression dynamics model with an evolving transcription network, whereas verifications by laboratory evolution experiments are also discussed. These results provide quantitative formulation on canalization and genetic assimilation, in terms of fluctuations of gene expression levels.