Quantifying Slow Evolutionary Dynamics in RNA Fitness Landscapes

TL;DR

This paper investigates the slow and punctuated nature of RNA evolution under directional selection, revealing that the approach to optimal structures is extremely gradual and out-of-equilibrium effects are minimal.

Contribution

It provides a detailed analysis of RNA fitness landscape dynamics, showing slow evolution and weak out-of-equilibrium effects during directional selection.

Findings

Evolution follows an inverse power law over time.

Out-of-equilibrium effects are very weak and hard to detect.

Transition genotypes near stasis borders have distinct mutational properties.

Abstract

We re-examine the evolutionary dynamics of RNA secondary structures under directional selection towards an optimum RNA structure. We find that the punctuated equilibria lead to a very slow approach to the optimum, following on average an inverse power of the evolutionary time. In addition, our study of the trajectories shows that the out-of-equilibrium effects due to the evolutionary process are very weak. In particular, the distribution of genotypes is close to that arising during equilibrium stabilizing selection. As a consequence, the evolutionary dynamics leave almost no measurable out-of-equilibrium trace, only the transition genotypes (close to the border between different periods of stasis) have atypical mutational properties.