Adaptation costs to constant and alternating polluted environments.

Area of Science:

• Evolutionary biology
• Environmental science
• Toxicology

Background:

• Anthropogenic stressors can drive rapid adaptation in populations.
• Understanding adaptation costs is crucial for assessing the evolution of resistance to environmental challenges.
• Experimental evolution provides a framework for studying adaptive responses to novel conditions.

Purpose of the Study:

• To investigate the evolutionary responses and associated costs in Caenorhabditis elegans populations exposed to uranium and salt.
• To assess how adaptation to single stressors (uranium or salt) affects fitness in novel environments.
• To determine the adaptive costs or benefits for populations evolved under alternating uranium/salt stress.

Main Methods:

• Experimental evolution of Caenorhabditis elegans populations over 22 generations under uranium, salt, and alternating uranium/salt conditions.
• Common-garden and reciprocal-transplant experiments to evaluate fitness.
• Comparison of life history characteristics and fitness across different treatment groups and control populations.

Main Results:

• Rapid evolutionary changes in life history were observed in response to pollutants.
• Populations adapted to pollutants showed reduced fitness in their original environments compared to controls, indicating adaptive costs.
• Adaptation to uranium or salt influenced fitness differently when exposed to the other stressor; alternating stress populations showed comparable or enhanced fitness.

Conclusions:

• Adaptive evolution to one stressor can result in costs or benefits when encountering a different stressor.
• Adaptation to alternating stressors did not incur additional costs.
• Adaptive cost assessments are essential for accurate ecological risk evaluations of pollutants.