Stress-Induced Mutagenesis and Complex Adaptation

TL;DR

This paper models how stress-induced mutagenesis enhances complex adaptation in asexual populations, breaking the usual trade-off between adaptability and stability, with theoretical predictions supporting its evolutionary advantage.

Contribution

It provides a theoretical framework showing stress-induced mutagenesis increases adaptation rates without fitness costs, a novel insight into mutation strategies.

Findings

Stress-induced mutagenesis accelerates complex adaptation.

It does not reduce the population's mean fitness.

Theoretical predictions quantify adaptation rates under different mutational strategies.

Abstract

Because mutations are mostly deleterious, mutation rates should be reduced by natural selection. However, mutations also provide the raw material for adaptation. Therefore, evolutionary theory suggests that the mutation rate must balance between adaptability - the ability to adapt - and adaptedness - the ability to remain adapted. We model an asexual population crossing a fitness valley and analyze the rate of complex adaptation with and without stress-induced mutagenesis - the increase of mutation rates in response to stress or maladaptation. We show that stress-induced mutagenesis increases the rate of complex adaptation without reducing the population mean fitness, thus breaking the evolutionary trade-off between adaptability and adaptedness. Our theoretical results support the hypothesis that stress-induced mutagenesis promotes adaptation and provide quantitative predictions of the rate of complex adaptation with different mutational strategies.