Adaptation dynamics of the quasispecies model

TL;DR

This paper analyzes how populations evolve on complex fitness landscapes, revealing a punctuated pattern of adaptation characterized by jumps between local peaks until reaching the global maximum, using an exact analytical approach.

Contribution

It provides an exact analytical study of quasispecies adaptation dynamics on rugged fitness landscapes within a simplified model.

Findings

Populations exhibit step-like jumps between fitness peaks.

The model predicts the time spent at local peaks before moving on.

The analysis identifies conditions for reaching the global maximum.

Abstract

We study the adaptation dynamics of an initially maladapted population evolving via the elementary processes of mutation and selection. The evolution occurs on rugged fitness landscapes which are defined on the multi-dimensional genotypic space and have many local peaks separated by low fitness valleys. We mainly focus on the Eigen's model that describes the deterministic dynamics of an infinite number of self-replicating molecules. In the stationary state, for small mutation rates such a population forms a {\it quasispecies} which consists of the fittest genotype and its closely related mutants. The quasispecies dynamics on rugged fitness landscape follow a punctuated (or step-like) pattern in which a population jumps from a low fitness peak to a higher one, stays there for a considerable time before shifting the peak again and eventually reaches the global maximum of the fitness landscape. We calculate exactly several properties of this dynamical process within a simplified version of the quasispecies model.