title: Association mapping of morphological traits in wild and captive zebra finches: reliable within, but not between populations.
abstract: Identifying causal genetic variants underlying heritable phenotypic variation is a long-standing goal in evolutionary genetics. We previously identified several quantitative trait loci (QTL) for five morphological traits in a captive population of zebra finches (Taeniopygia guttata) by whole-genome linkage mapping. We here follow up on these studies with the aim to narrow down on the quantitative trait variants (QTN) in one wild and three captive populations. First, we performed an association study using 672 single nucleotide polymorphisms (SNPs) within candidate genes located in the previously identified QTL regions in a sample of 939 wild-caught zebra finches. Then, we validated the most promising SNP-phenotype associations (n = 25 SNPs) in 5228 birds from four populations. Genotype-phenotype associations were generally weak in the wild population, where linkage disequilibrium (LD) spans only short genomic distances. In contrast, in captive populations, where LD blocks are large, apparent SNP effects on morphological traits (i.e. associations) were highly repeatable with independent data from the same population. Most of those SNPs also showed significant associations with the same trait in other captive populations, but the direction and magnitude of these effects varied among populations. This suggests that the tested SNPs are not the causal QTN but rather physically linked to them, and that LD between SNPs and causal variants differs between populations due to founder effects. While the identification of QTN remains challenging in nonmodel organisms, we illustrate that it is indeed possible to confirm the location and magnitude of QTL in a population with stable linkage between markers and causal variants.
authors.affiliation: Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, 82319, Seewiesen, Germany.
authors.forename: Ulrich
authors.identifier: http://orcid.org/0000-0001-6959-3033
authors.initials: U
authors.lastname: Knief
authors.affiliation: Department of Population Ecology, Friedrich Schiller University Jena, 07743, Jena, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Schielzeth
authors.affiliation: Department of Ecology and Genetics, Uppsala University, 752 36, Uppsala, Sweden.
authors.forename: Niclas
authors.initials: N
authors.lastname: Backström
authors.affiliation: Institute of Clinical Molecular Biology, Christian-Albrechts-University, 24105, Kiel, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Hemmrich-Stanisak
authors.affiliation: Institute of Clinical Molecular Biology, Christian-Albrechts-University, 24105, Kiel, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Wittig
authors.affiliation: Institute of Clinical Molecular Biology, Christian-Albrechts-University, 24105, Kiel, Germany.
authors.forename: Andre
authors.initials: A
authors.lastname: Franke
authors.affiliation: Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia.|School of Biological, Earth & Environmental Sciences, University of New South Wales, Sydney, NSW, 2057, Australia.
authors.forename: Simon C
authors.initials: SC
authors.lastname: Griffith
authors.affiliation: Department of Ecology and Genetics, Uppsala University, 752 36, Uppsala, Sweden.
authors.forename: Hans
authors.initials: H
authors.lastname: Ellegren
authors.affiliation: Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, 82319, Seewiesen, Germany.
authors.forename: Bart
authors.initials: B
authors.lastname: Kempenaers
authors.affiliation: Department of Behavioural Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, 82319, Seewiesen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Forstmeier
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D046369:Finches / Q000033:anatomy & histology / Q000235:genetics*; D005828:Genetics, Population; D005838:Genotype; D015810:Linkage Disequilibrium; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci
keywords: association study; genotype-phenotype maps; linkage mapping; morphology; quantitative trait locus; standing genetic variation