"Excluded phenotypes" restrict genetic paths toward adaptation in declining populations.

Area of Science:

• Evolutionary biology
• Population genetics

Background:

• Evolutionary rescue is crucial for species survival amid environmental change.
• Mutations can aid adaptation, but their effectiveness depends on population dynamics.

Purpose of the Study:

• To investigate the role of an
• evolutionary excluded zone
• in hindering evolutionary rescue.
• To experimentally test if specific mutations are inaccessible to declining populations.
• To integrate findings into Fisher's Geometric Model for broader applicability.

Main Methods:

• Experimental evolution using M13 bacteriophage populations under declining conditions.
• Analysis of mutant phenotypes and their impact on population growth.
• Integration with Fisher's Geometric Model to simulate evolutionary trajectories.

Main Results:

• An
• evolutionary excluded zone
• was experimentally confirmed in M13 bacteriophage.
• Certain beneficial mutations were found to be inaccessible, preventing evolutionary rescue.
• The excluded zone significantly reduces rescue probability via de novo mutation.

Conclusions:

• Evolutionary rescue is more complex in declining populations due to the excluded zone.
• The dynamics of evolution differ fundamentally between declining and stable/growing populations.
• Understanding these excluded zones is critical for predicting species' responses to environmental stress.