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BP: Fachverband Biologische Physik

BP 21: Focus Session: Sequence Spaces, Populations and Evolution

BP 21.4: Hauptvortrag

Mittwoch, 11. März 2026, 16:15–16:45, HÜL/S386

The navigability of fitness landscapes shaped by global and universal epistasis — •Joachim Krug — Institute for Biological Physics, University of Cologne, Germany

Epistasis is the dependence of the effect of a mutation on the genetic context in which it occurs. Epistatic interactions shape the topography of the fitness landscape, the mapping from genotype to reproductive success. Global epistasis refers to interactions that arise when a nonlinear phenotype-fitness map acts on a lower-dimensional set of non-epistatic phenotypes, and has been argued to be a common occurrence at different scales of biological organization. It is therefore of interest to ask what features characterize fitness landscapes when epistasis is purely global. Here I show that, under certain conditions, global epistasis implies universal negative epistasis [1], an order relation on sequence space that is closely related to submodularity of set functions [2]. Universal epistasis makes fitness landscapes easily navigable, because any fitness peak is accessible through combinatorially many fitness-increasing mutational paths. I will discuss the theoretical results within the context of recent studies of large-scale empirical fitness landscapes that have found that rugged landscapes may also be highly navigable.

[1] Krug, J. & Oros, D.: Evolutionary accessibility of random and structured fitness landscapes. J. Stat. Mech. 034003:2024

[2] Pahujani, S. & Krug, J.: Complexity and accessibility of random landscapes. arXiv:2502.05896

Keywords: fitness landscape; experimental evolution; epistasis