Epistasis and Adaptation on Fitness Landscapes

TL;DR

This paper reviews how epistasis influences evolution by analyzing fitness landscapes, combining theoretical insights with empirical data to understand its role in adaptation and highlighting future research directions.

Contribution

It synthesizes fitness landscape theory and empirical findings to clarify epistasis's role in evolution and discusses open challenges for integrating data and theory.

Findings

Epistasis is prevalent in fitness landscapes.

Fitness effects depend on environment and mutations.

Empirical landscapes reveal complex epistatic interactions.

Abstract

Epistasis occurs when the effect of a mutation depends on its carrier's genetic background. Despite increasing evidence that epistasis for fitness is common, its role during evolution is contentious. Fitness landscapes, mappings of genotype or phenotype to fitness, capture the full extent and complexity of epistasis. Fitness landscape theory has shown how epistasis affects the course and the outcome of evolution. Moreover, by measuring the competitive fitness of sets of tens to thousands of connected genotypes, empirical fitness landscapes have shown that epistasis is frequent and depends on the fitness measure, the choice of mutations for the landscape, and the environment in which it was measured. Here, I review fitness landscape theory and experiments and their implications for the role of epistasis in adaptation. I discuss theoretical expectations in the light of empirical fitness landscapes and highlight open challenges and future directions towards integrating theory and data, and incorporating ecological factors.