Evolutionary Rescue over a Fitness Landscape

Area of Science:

• Evolutionary biology
• Population genetics
• Conservation science

Background:

• Evolutionary rescue is crucial for preventing population extinction under environmental stress.
• Existing models often overlook how stress impacts adaptation speed.
• Fisher's geometric model provides a framework to study environment-dependent mutation fitness effects.

Purpose of the Study:

• To investigate the impact of environmental stress on the speed of adaptation during evolutionary rescue.
• To develop a predictive model for evolutionary rescue incorporating stress-dependent evolutionary effects.
• To identify key parameters influencing rescue probability across stress gradients.

Main Methods:

• Utilized Fisher's geometric model of adaptation.
• Derived analytic results under a strong-selection-weak-mutation regime.
• Compared analytic predictions with simulation results.

Main Results:

• Introduced a composite parameter quantifying effective stress level, measurable empirically.
• Identified a narrow characteristic stress window where rescue probability drops sharply.
• Demonstrated that decreasing proportions of stress-resistant mutations with increasing stress sharpen this probability drop.

Conclusions:

• The effective stress level parameter simplifies understanding of environmental effects on evolutionary rescue.
• The identified narrow stress window has implications for predicting extinction risk and managing resistant populations.
• Experimental validation using rescue experiments across stress gradients is proposed.