Adaptive tracking with antagonistic pleiotropy results in seemingly neutral molecular evolution.

Area of Science:

• Evolutionary biology
• Molecular evolution
• Genomics

Background:

• The neutral theory of molecular evolution suggests most amino acid substitutions are neutral.
• This theory is widely supported by comparative genomic data.
• A key premise is the scarcity of beneficial mutations.

Purpose of the Study:

• To challenge the scarcity premise of the neutral theory.
• To propose a new evolutionary theory compatible with high beneficial mutation rates.
• To explain how neutral substitutions can prevail despite frequent adaptation.

Main Methods:

• Deep mutational scanning of 12,267 mutations across 24 genes.
• Population genetics simulations.
• Empirical observations and experimental evolution.

Main Results:

• >1% of mutations were found to be beneficial.
• This suggests >99% of amino acid substitutions could be adaptive.
• A new theory, adaptive tracking with antagonistic pleiotropy, was proposed.

Conclusions:

• Frequent environmental changes and antagonistic pleiotropy limit the fixation of beneficial mutations.
• Neutral substitutions prevail despite continuous adaptation (adaptive tracking).
• The proposed theory explains evolutionary dynamics and implications for natural populations.