Adapting to an increasingly stressful environment: Experimental evidence for 'micro-evolutionary priming'

Area of Science:

• Ecology
• Evolutionary Biology
• Environmental Science

Background:

• Natural populations face increasing environmental stress with fluctuating intensities.
• Micro-evolutionary adaptation can help populations cope with gradual stress increases.
• Adaptation to low stress may not prevent population collapse during acute stress events.

Purpose of the Study:

• To test the concept of 'micro-evolutionary priming' in populations exposed to varying copper stress levels.
• To investigate if adaptation to low stress enhances tolerance to acute, higher stress.
• To assess the impact of prior stress exposure on population growth performance.

Main Methods:

• A multigenerational selection experiment using the rotifer Brachionus calyciflorus exposed to four copper concentrations (control, low, intermediate, high).
• A subsequent common garden experiment assessing population growth performance across generations.
• Randomly selected genotypes from selected populations were exposed to different copper levels.

Main Results:

• Populations previously exposed to copper, even at low levels, showed significantly better performance under intermediate and high copper stress compared to control populations.
• Control populations experienced severe growth reductions and high mortality when exposed to intermediate and high copper levels.
• Fitness differences were minimal at low copper levels, but populations pre-exposed to low copper strongly outperformed controls at higher levels.

Conclusions:

• Micro-evolutionary priming, or adaptation to low stress, can significantly enhance population resilience to acute environmental challenges.
• This phenomenon has potentially strong, overlooked implications for population persistence and eco-evolutionary dynamics in changing environments.
• Understanding micro-evolutionary priming is vital for predicting species' responses to environmental fluctuations and stress.