Genetic incompatibilities are widespread within species

Area of Science:

• Evolutionary genetics
• Population genetics
• Genomics

Background:

• Epistasis (non-additive allele interactions) is crucial for population fitness but empirically challenging to study.
• Traditional methods infer epistasis from trait-specific genotypic value non-independence.
• Epistasis for fitness should leave a detectable genomic footprint.

Purpose of the Study:

• To develop and apply a novel method for detecting epistasis based on genotype ratio distortion.
• To empirically confirm genotype ratio distortion as a signature of epistatic fitness effects.
• To assess the prevalence of epistasis in a population of Drosophila melanogaster.

Main Methods:

• Developed a method to detect genotype ratio distortion as an indicator of epistasis.
• Applied this method to a large panel of Drosophila melanogaster recombinant inbred lines.
• Experimentally confirmed the link between genotype ratio distortion and epistatic fitness effects.

Main Results:

• Confirmed that genotype ratio distortion signifies loci with epistatic fitness effects.
• Estimated that any two haploid genomes in the study harbor an average of 1.15 pairs of epistatically interacting alleles.
• Demonstrated that epistasis is widespread and may often be undetected.

Conclusions:

• Epistasis is a common force shaping fitness and is readily detectable through genotype ratio distortion.
• The prevalence of epistasis provides raw material for reproductive isolation, impacting speciation genetics.
• Findings challenge the necessity of allopatric mutation divergence for reproductive isolation, highlighting contemporary within-species genetic variation.