Large effect loci have a prominent role in Darwin's finch evolution

A fundamental goal in evolutionary biology is to understand the genetic architecture of adaptive traits and its evolutionary relevance. Using whole-genome data of 3,958 Darwins finches on the Galapagos Island of Daphne Major we identify six loci of large effect that explain 46% of the variation in beak size of Geospiza fortis, a key ecological trait. Allele frequency changes across 30 years at these loci affected beak morphology in two ways. An abrupt change in beak size occurred in Geospiza fortis as a result of natural selection associated with a drought, and a more gradual change occurred in G. scandens as a result of introgressive hybridization. This study demonstrates how large effect loci are a major contributor to the genetic architecture of rapid diversification during adaptive radiations. One Sentence SummaryAllele frequency change at six loci of large effect causes evolutionary change in key ecological traits.