Supergene Evolution Triggered by the Introgression of a Chromosomal Inversion

Area of Science:

• Evolutionary genetics
• Population genetics
• Genomics

Background:

• Supergenes are genetic architectures for complex traits under balancing selection.
• They involve tightly linked loci inherited as a single locus, often maintained by suppressed recombination.
• The formation mechanism of supergenes remains poorly understood, posing a paradox for divergent haplotype establishment.

Purpose of the Study:

• To investigate the mechanism behind supergene formation.
• To understand the evolution of mimicry polymorphism in Heliconius numata butterflies.
• To explore the role of chromosomal rearrangements in supergene evolution.

Main Methods:

• Analysis of haplotype divergence and linkage disequilibrium.
• Investigation of chromosomal rearrangements, specifically inversions.
• Comparative genomic analysis of Heliconius numata.

Main Results:

• Supergene allele formation in Heliconius numata is linked to the introgression of a divergent, inverted chromosomal segment.
• Supergene alleles evolved from chromosomal inversions captured by introgression, maintained by balanced polymorphism.
• Evidence suggests over a million years of independent chromosomal evolution in separate lineages.

Conclusions:

• Introgression of chromosomal rearrangements is a key mechanism in supergene formation.
• This process facilitates the evolution of complex structural polymorphisms and adaptive syndromes.
• Reticulation of genealogies significantly influences the evolution of genetic architectures.