Does environmental robustness play a role in fluctuating environments?

Area of Science:

• Evolutionary biology
• Quantitative genetics
• Environmental adaptation

Background:

• Fluctuating environments are predicted to favor genetic robustness in fitness.
• Previous quantitative genetic studies have not fully tested these predictions.
• Understanding adaptation to environmental variability is crucial for predicting species' responses to climate change.

Purpose of the Study:

• To investigate the genetic basis of adaptation to fluctuating thermal environments in Drosophila melanogaster.
• To determine whether genetic correlations support the prediction that environmental robustness or average fitness predicts fitness in fluctuating environments.
• To estimate genetic variance for egg-to-adult viability under different temperature regimes.

Main Methods:

• Utilized a full-sib, half-sib breeding design in Drosophila melanogaster.
• Assessed egg-to-adult viability across constant (25°C, 30°C) and fluctuating temperature conditions.
• Estimated breeding values for environmental robustness (reaction norm slope) and average viability (reaction norm elevation).

Main Results:

• Genetic correlations revealed that average viability across constant environments was a key predictor of fitness in fluctuating environments.
• Environmental robustness (reaction norm slope) was not the primary factor explaining fitness in fluctuating thermal conditions.
• Results indicate that adaptation to fluctuating environments may be more strongly influenced by general viability than specialized robustness.

Conclusions:

• Average genetic fitness across environments, rather than environmental robustness, is critical for adaptation to fluctuating thermal conditions.
• The importance of environmental robustness in adaptation to fluctuating environments may be overestimated.
• Findings provide novel insights into the genetic architecture of adaptation to environmental variability in ectotherms.