From valleys to peaks: The role of evolvability in fitness landscape navigation.

Understanding the balance between evolvability and mutational robustness is crucial for exploring adaptation in complex fitness landscapes. This study examines how heterogeneous populations adapt under varying mutation rates (μ) and fitness landscape ruggedness (K), emphasizing their distinct starting conditions in valleys, slopes (low prominence), or peaks (high prominence). Using an extended NK model, we simulate populations capable of initiating anywhere in the landscape. Our findings reveal that starting positions strongly influence whether robustness or evolvability is advantageous. Populations beginning in low-prominence regions (valleys and slopes) exhibited high levels of epistasis ( $ϵ$ ) and pleiotropy (π), enhancing evolvability and enabling exploration of the fitness landscape. In contrast, populations starting in high-prominence regions (peaks) reduced $ϵ$ and π, prioritizing robustness to maintain stability against mutations. This study highlights the role of starting conditions in shaping evolutionary trajectories, offering insights into the interplay between evolvability and robustness.