Adaptive walks toward a moving optimum

Area of Science:

• Evolutionary biology
• Genetics
• Biophysics

Background:

• Natural selection drives adaptation.
• Environmental changes can be gradual or sudden.
• Understanding adaptation dynamics is crucial for predicting evolutionary trajectories.

Purpose of the Study:

• To investigate how environmental change speed affects adaptation dynamics and outcomes.
• To model adaptive walks using RNA sequences under varying temperature changes.
• To compare evolutionary responses to gradual versus sudden environmental shifts.

Main Methods:

• Simulated adaptive walks in monomorphic lineages.
• Used short RNA sequences selected for stability and structure conservation.
• Varied the speed of environmental change (increasing temperature).

Main Results:

• Slower environmental change reduced the fitness effect of beneficial mutations.
• Adaptation to slower change led to fitter endpoints with fewer possible phenotypes.
• The timing of major evolutionary substitutions shifted with change speed.

Conclusions:

• Gradual environmental changes yield different adaptive outcomes than sudden changes.
• Predictions from sudden environmental change experiments may not apply to gradual changes.
• Environmental stability is a key factor influencing the speed and direction of evolution.