Avoiding dead ends: the experimental evolution of constraint as adaptation to environmental variation

Area of Science:

• Evolutionary Biology
• Genetics
• Microbiology

Background:

• Bet-hedging traits enhance long-term fitness in unpredictable environments but are suboptimal short-term.
• The persistence of bet hedging is puzzling as selection should eliminate suboptimal traits in benign conditions.

Purpose of the Study:

• To test the hypothesis that bet hedging to rare, severe events persists due to evolved constraints on short-term adaptation.
• To investigate the role of evolutionary constraints in maintaining bet-hedging strategies.

Main Methods:

• Experimental evolution of Saccharomyces cerevisiae strains under decreasing frequencies of extreme heat shocks.
• Comparing adaptation rates to benign conditions between strains evolved under different heat shock regimes.

Main Results:

• Strains evolved under severe, infrequent heat shocks showed constrained adaptation to benign conditions.
• This constraint made them less susceptible to short-term environmental changes.

Conclusions:

• Evolutionary constraint can be an adaptive mechanism, enabling the persistence of bet hedging.
• This provides a solution to the paradox of bet hedging requiring apparent maladaptation.