Origins of the Fittest: Clonal Interference in Heterogeneous Networks

In asexual populations, clonal interference, the competition between strains carrying different beneficial mutations, plays a crucial role in shaping evolutionary outcomes. This study investigates how this phenomenon unfolds in complex heterogeneous networks, demonstrating that network structure significantly affects the origin and spread of high-fitness strains. Using computational modeling and a novel analytical approach, we demonstrate that the interplay between mutation rates and network topology creates distinct evolutionary regimes. We observe that the mutations driving adaptation originate from network locations that facilitate mutation spread within a time-frame given by the mutation rate. If the window widens or narrows, the contribution of different network regions grows or diminishes. Using analytical approaches from epidemic modeling and network geometry, our analysis efficiently captures this evolutionary dynamic in arbitrary network configurations. This work provides new insights into how spatial heterogeneity shapes evolutionary trajectories and indicates that attempts to alter the speed of adaptation through network modifications will succeed or fail depending critically on the prevailing evolutionary regime—insights relevant to epidemiology, conservation biology, and beyond.