Repeatability of evolution on epistatic landscapes

TL;DR

This paper explores how epistatic interactions influence evolutionary pathways, especially under varying mutation rates and population dynamics, revealing complex behaviors beyond traditional models.

Contribution

It introduces a theoretical and computational framework that accounts for epistasis affecting both fitness and mutation rates, extending beyond the strong selection, weak mutation regime.

Findings

Epistatic effects can alter mutational path probabilities.

Pathways previously considered negligible can become accessible.

Results align more closely with experimental observations.

Abstract

Evolution is a dynamic process. The two classical forces of evolution are mutation and selection. Assuming small mutation rates, evolution can be predicted based solely on the fitness differences between phenotypes. Predicting an evolutionary process under varying mutation rates as well as varying fitness is still an open question. Experimental procedures, however, do include these complexities along with fluctuating population sizes and stochastic events such as extinctions. We investigate the mutational path probabilities of systems having epistatic effects on both fitness and mutation rates using a theoretical and computational framework. In contrast to previous models, we do not limit ourselves to the typical strong selection, weak mutation (SSWM)-regime or to fixed population sizes. Rather we allow epistatic interactions to also affect mutation rates. This can lead to qualitatively non-trivial dynamics. Pathways, that are negligible in the SSWM-regime, can overcome fitness valleys and become accessible. This finding has the potential to extend the traditional predictions based on the SSWM foundation and bring us closer to what is observed in experimental systems.