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A beak size locus in Darwin’s finches facilitated character displacement during a drought

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Science  22 Apr 2016:
Vol. 352, Issue 6284, pp. 470-474
DOI: 10.1126/science.aad8786

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Linked loci and Galapagos finch size

Observations of parallel evolution in the finches of the Galapagos, including body and beak size, contributed to Darwin's theories. Lamichhaney et al. carried out whole-genome sequencing of 60 Darwin's finches. These included small, medium, and large ground finches as well as small, medium, and large tree finches. A genomic region containing the HMGA2 gene correlated strongly with beak size across different species. This locus appears to have played a role in beak diversification throughout the radiation of Darwin's finches.

Science, this issue p. 470

Abstract

Ecological character displacement is a process of morphological divergence that reduces competition for limited resources. We used genomic analysis to investigate the genetic basis of a documented character displacement event in Darwin’s finches on Daphne Major in the Galápagos Islands: The medium ground finch diverged from its competitor, the large ground finch, during a severe drought. We discovered a genomic region containing the HMGA2 gene that varies systematically among Darwin’s finch species with different beak sizes. Two haplotypes that diverged early in the radiation were involved in the character displacement event: Genotypes associated with large beak size were at a strong selective disadvantage in medium ground finches (selection coefficient s = 0.59). Thus, a major locus has apparently facilitated a rapid ecological diversification in the adaptive radiation of Darwin’s finches.

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