Weak antagonistic fitness effects can maintain an inversion polymorphism

Area of Science:

• Evolutionary genetics
• Population genetics
• Genomics

Background:

• Chromosomal inversions are key to evolutionary adaptation.
• Understanding the maintenance of polymorphisms with weak fitness effects is crucial.
• Zebra finch chromosome Tgu11 harbors a significant inversion polymorphism.

Purpose of the Study:

• Investigate the maintenance mechanisms of a weak-effect chromosomal inversion polymorphism.
• Quantify the fitness effects of the Tgu11 inversion in zebra finches.
• Determine the long-term stability of this inversion polymorphism.

Main Methods:

• Analysis of fitness-related traits in over 6000 captive zebra finches.
• Estimation of additive and recessive fitness effects of the inversion alleles.
• Individual-based simulations to model polymorphism dynamics.

Main Results:

• The inverted allele D conferred small, additive benefits to male siring success and female fecundity.
• Homozygotes for the D allele exhibited slightly reduced survival rates.
• Simulations indicated potential stabilization at intermediate frequencies due to weak net heterosis.

Conclusions:

• Antagonistic fitness effects can maintain chromosomal inversion polymorphisms.
• The Tgu11 inversion polymorphism may be stabilized by weak net heterosis.
• Further studies in free-living populations are needed to validate findings and assess fixation potential.