Can deleterious mutations explain the time dependency of molecular rate estimates?

Area of Science:

• Evolutionary biology
• Population genetics
• Molecular evolution

Background:

• Recent studies indicate that molecular evolution rates appear to increase over shorter time spans.
• This phenomenon, termed rate acceleration, has been observed in molecular evolutionary studies.

Purpose of the Study:

• To investigate if deleterious mutations alone can account for the observed rate acceleration in molecular evolution.
• To derive empirical approximations for mutation persistence and estimate lower limits on effective population sizes.

Main Methods:

• Derivation of an empirical approximation for the persistence of deleterious mutations in a randomly mating population.
• Calculation of lower limits on effective population sizes based on mutation persistence.

Main Results:

• The derived lower limits for effective population sizes are high.
• These limits increase further with additional reasonable assumptions.

Conclusions:

• The high estimated effective population sizes cast doubt on deleterious mutations as the sole explanation for the apparent rate acceleration in molecular evolution.
• Alternative or additional mechanisms may be required to fully explain the observed phenomenon.