The Baldwin effect under multi-peaked fitness landscapes: Phenotypic fluctuation accelerates evolutionary rate

TL;DR

This study analytically demonstrates that phenotypic fluctuation accelerates evolutionary rates on multi-peaked fitness landscapes but reduces average fitness, highlighting a trade-off that influences adaptive evolution.

Contribution

It provides analytical expressions for evolutionary rate and fitness, confirming phenotypic fluctuation's accelerating effect on evolution in complex landscapes.

Findings

Phenotypic fluctuation always accelerates evolutionary rate.

Phenotypic fluctuation decreases average population fitness.

Accelerates error catastrophe in high-fitness peaks.

Abstract

Phenotypic fluctuations and plasticity can generally affect the course of evolution, a process known as the Baldwin effect. Several studies have recast this effect and claimed that phenotypic plasticity acceler- ates evolutionary rate (the Baldwin expediting effect); however, the validity of this claim is still controversial. In this study, we investi- gate the evolutionary population dynamics of a quantitative genetic model under a multi-peaked fitness landscape, in order to evaluate the validity of the effect. We provide analytical expressions for the evolutionary rate and average population fitness. Our results indicate that under a multi-peaked fitness landscape, phenotypic fluctuation always accelerates evolutionary rate, but it decreases the average fit- ness. As an extreme case of the trade-off between the rate of evolution and average fitness, phenotypic fluctuation is shown to accelerate the error catastrophe, in which a population fails to sustain a high-fitness peak. In the context of our findings, we discuss the role of phenotypic plasticity in adaptive evolution.