Antagonistic pleiotropy conceals molecular adaptations in changing environments

Area of Science:

• Molecular Evolution
• Evolutionary Biology
• Genomics

Background:

• The role of positive selection in molecular evolution is debated, with lab studies showing frequent adaptation while natural evolution suggests otherwise.
• This discrepancy may stem from environmental changes in nature, where mutations beneficial at one time can become deleterious due to antagonistic pleiotropy.

Purpose of the Study:

• To investigate the impact of changing environments on the rate of molecular adaptation.
• To test the hypothesis that environmental fluctuations hinder the fixation of beneficial mutations, leading to an underestimation of positive selection in natural populations.

Main Methods:

• Yeast evolution experiments were conducted in both changing and constant environments.
• Genome sequencing was used to analyze the evolving populations and quantify mutation rates.
• Population genetic simulations were performed to support the experimental findings.

Main Results:

• The ratio of nonsynonymous to synonymous nucleotide changes was lower in changing environments compared to constant ones.
• Population dynamics of mutations supported the hypothesis that environmental changes impede adaptation.
• Antagonistic fitness effects of mutations in dynamic environments were observed.

Conclusions:

• Environmental variability in nature can lead to an underestimation of molecular adaptation.
• Antagonistic pleiotropy in fluctuating environments significantly impacts the fixation of mutations.
• The true rate of positive selection in natural populations may be higher than currently inferred from genomic data.