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

James S Andon1, Charles D Kocher2,3, Ken A Dill2,3,4

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Proceedings of the National Academy of Sciences of the United States of America
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Declining populations face an "evolutionary excluded zone" where certain beneficial mutations hinder rescue. This significantly reduces the chances of evolutionary rescue by new mutations, altering evolution dynamics.

Keywords:
Geometric ModelPACEevolutionary rescueexcluded zone

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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.