The pace of evolution across fitness valleys

TL;DR

This paper investigates the speed at which asexual populations evolve across fitness valleys, analyzing how mutation order, population size, fitness, and mutation rate influence the time to reach higher fitness peaks.

Contribution

It provides a theoretical analysis of the evolution dynamics across fitness valleys considering different mutation orders and population parameters.

Findings

Fixed mutation order leads to faster evolution along a single path.

Random mutation order results in multiple evolutionary pathways with varying times.

Population size and mutation rate significantly affect the fixation time.

Abstract

How fast does a population evolve from one fitness peak to another? We study the dynamics of evolving, asexually reproducing populations in which a certain number of mutations jointly confer a fitness advantage. We consider the time until a population has evolved from one fitness peak to another one with a higher fitness. The order of mutations can either be fixed or random. If the order of mutations is fixed, then the population follows a metaphorical ridge, a single path. If the order of mutations is arbitrary, then there are many ways to evolve to the higher fitness state. We address the time required for fixation in such scenarios and study how it is affected by the order of mutations, the population size, the fitness values and the mutation rate.