A cryptic rock-paper-scissors game between Drosophila males

Area of Science:

• Evolutionary Biology
• Genetics
• Sexual Selection

Background:

• Maintaining genetic variation in fitness-related traits is a key evolutionary question.
• Laboratory fruit fly populations show unexpected fitness variation, suggesting complex selection or genetic architecture.
• Postcopulatory sexual selection, particularly sperm competition, is a critical component of male fitness.

Purpose of the Study:

• To investigate the role of nontransitive interactions in maintaining genetic variation during sperm competition in Drosophila.
• To identify the genetic basis of these non-transitive sexual selection outcomes.
• To understand the mechanisms promoting stable polymorphism in fitness traits.

Main Methods:

• Utilized chromosome extraction lines in Drosophila melanogaster.
• Analyzed postcopulatory sexual selection outcomes, specifically sperm competition between males with different genotypes.
• Applied principles of the rock-paper-scissors (RPS) game model to understand selection dynamics.

Main Results:

• Demonstrated non-transitive interactions in sperm competition among male Drosophila, mirroring RPS dynamics.
• Confirmed that the outcome of sperm competition depends on the competitor male's genotype.
• Identified at least four genetic loci associated with these RPS-like cycles in sperm competition.

Conclusions:

• Nontransitive postcopulatory sexual selection can maintain genetic variation in male reproductive fitness.
• The identified genetic loci provide a foundation for understanding the molecular basis of this variation.
• These findings offer insights into the persistence of polymorphism in a critical fitness component.