Sexual selection, germline mutation rate and sperm competition.

Area of Science:

• Evolutionary Biology
• Genetics

Background:

• Sexual selection involves females choosing mates, often based on exaggerated traits, providing offspring viability benefits.
• Maintaining genetic variance in viability genes under strong directional selection is an evolutionary puzzle.
• Extra-pair paternity increases reproductive success variance and is linked to females seeking 'good genes'.

Purpose of the Study:

• To investigate the hypothesis that sexual selection is linked to elevated mutation rates.
• To explore how elevated mutation rates might maintain genetic variance in viability despite directional selection.
• To test potential mechanisms for elevated mutation, such as sperm competition and mutator alleles.

Main Methods:

• Comparative study of birds examining mutation rates at minisatellite loci.
• Correlating mutation rates with measures of extra-pair paternity and relative testes mass.
• Assessing the relationship between mutation rates and longevity to infer mutation origin (meiotic vs. mitotic).

Main Results:

• A positive correlation was found between mutation rate at minisatellite loci and extra-pair paternity in birds.
• Mutation rates were not correlated with relative testes mass, suggesting sperm production is not the driver.
• Minisatellite mutation rates did not correlate with longevity, indicating a meiotic origin.

Conclusions:

• Species with more intense sexual selection exhibit increased mutation rates.
• Elevated mutation rates are not linked to increased sperm production.
• Intense sexual selection may sustain high mutation rates by continually favoring viability alleles, which in turn increases genetic variance and enhances sexual selection benefits.