A supergene and genomic mosaicism are associated with phenotypic evolution in Galápagos tree finches.

A supergene called G03 is linked to beak and body size differences, with its divergence enabling phenotypic shifts in Camarhynchus finches despite shallow overall genetic divergence.

• Why it matters: Understanding how phenotypic diversity arises with limited genetic differentiation can shed light on speciation and adaptive radiation processes, especially in Darwin's finches.
• What they did: The study analyzed whole genomes and morphological data from Camarhynchus finches, identifying a supergene and revealing genomic mosaicism with autosomal differentiation mainly at G03, which approaches fixation.
• The result: The divergence of G03 haplotypes early in the radiation suggests it was a key genetic innovation for ecological expansion, highlighting hybridization's role in generating biodiversity among Darwin's finches.