Intralocus conflicts associated with a supergene

Area of Science:

• Evolutionary Biology
• Genetics
• Animal Behavior

Background:

• Chromosomal inversions are key drivers of phenotypic variation, often maintained by sexual selection.
• Supergenes, tightly linked sets of genes, can control distinct phenotypes, as seen in the ruff bird's mating morphs.
• Understanding the forces stabilizing such polymorphisms is crucial for evolutionary genetics.

Purpose of the Study:

• To investigate the role of intralocus conflicts in maintaining a specific autosomal inversion polymorphism in the ruff (Calidris pugnax).
• To assess how this inversion affects reproductive success in both male and female ruffs.
• To determine if balancing selection, driven by sexually antagonistic selection, stabilizes the supergene variants.

Main Methods:

• Analysis of reproductive success (laying rate, egg size, offspring survival) in a captive population of ruffs.
• Comparison of reproductive performance between females with different inversion haplotypes (Independent, Satellite, Faeder).
• Inference of fitness contributions based on observed reproductive output in females and inferred success in males.

Main Results:

• Faeder females, possessing a non-recombined inversion haplotype, exhibited lower reproductive success compared to Independent females (lacking the inversion).
• Satellite females, with a recombined inversion haplotype, showed intermediate reproductive performance.
• The reduced reproductive output of Faeder females is likely counterbalanced by higher reproductive success in Faeder males.

Conclusions:

• Intralocus conflicts, arising from sexually antagonistic selection, are a probable mechanism maintaining the inversion polymorphism in ruffs.
• This study highlights the significant role of balancing selection in the evolution and stability of supergene variants.
• The findings provide insights into the complex interplay between genetic architecture, sexual conflict, and phenotypic diversity.