Growth factor gene IGF1 is associated with bill size in the black-bellied seedcracker Pyrenestes ostrinus. Author Bridgett vonHoldt, Rebecca Kartzinel, Christian Huber, Vinh Le Underwood, Ying Zhen, Kristen Ruegg, Kirk Lohmueller, Thomas Smith Publication Year 2018 Type Journal Article Abstract Pyrenestes finches are unique among birds in showing a non-sex-determined polymorphism in bill size and are considered a textbook example of disruptive selection. Morphs breed randomly with respect to bill size, and differ in diet and feeding performance relative to seed hardness. Previous breeding experiments are consistent with the polymorphism being controlled by a single genetic factor. Here, we use genome-wide pooled sequencing to explore the underlying genetic basis of bill morphology and identify a single candidate region. Targeted resequencing reveals extensive linkage disequilibrium across a 300 Kb region containing the insulin-like growth factor 1 (IGF1) gene, with a single 5-million-year-old haplotype associating with phenotypic dominance of the large-billed morph. We find no genetic similarities controlling bill size in the well-studied Darwin's finches (Geospiza). Our results show how a single genetic factor may control bill size and provide a foundation for future studies to examine this phenomenon within and among avian species. Keywords Animals, Biological Evolution, Selection, Genetic, Phenotype, Gene Expression, Polymorphism, Genetic, Haplotypes, Linkage Disequilibrium, Insulin-Like Growth Factor I, Beak, Finches, Seeds, Eating, Hardness, Organ Size, Whole Genome Sequencing Journal Nat Commun Volume 9 Issue 1 Pages 4855 Date Published 2018 Nov 19 ISSN Number 2041-1723 DOI 10.1038/s41467-018-07374-9 Alternate Journal Nat Commun PMCID PMC6242981 PMID 30451848 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML