title: A novel locus on chromosome 1 underlies the evolution of a melanic plumage polymorphism in a wild songbird.
abstract: Understanding the mechanisms responsible for phenotypic diversification within and among species ultimately rests with linking naturally occurring mutations to functionally and ecologically significant traits. Colour polymorphisms are of great interest in this context because discrete colour patterns within a population are often controlled by just a few genes in a common environment. We investigated how and why phenotypic diversity arose and persists in theZosterops borbonicuswhite-eye of Reunion (Mascarene archipelago), a colour polymorphic songbird in which all highland populations contain individuals belonging to either a brown or a grey plumage morph. Using extensive phenotypic and genomic data, we demonstrate that this melanin-based colour polymorphism is controlled by a single locus on chromosome 1 with two large-effect alleles, which was not previously described as affecting hair or feather colour. Differences between colour morphs appear to rely upon complexcis-regulatory variation that either prevents the synthesis of pheomelanin in grey feathers, or increases its production in brown ones. We used coalescent analyses to show that, from a 'brown' ancestral population, the dominant 'grey' allele spread quickly once it arose from a new mutation. Since colour morphs are always found in mixture, this implies that the selected allele does not go to fixation, but instead reaches an intermediate frequency, as would be expected under balancing selection.
authors.affiliation: Laboratoire Évolution et Diversité Biologique , UMR5174 CNRS, Université Paul Sabatier - ENFA , 31062 Toulouse Cedex 9 , France.
authors.forename: Yann X C
authors.identifier: 0000-0002-1809-387X
authors.initials: YX
authors.lastname: Bourgeois
authors.affiliation: Laboratoire Évolution et Diversité Biologique , UMR5174 CNRS, Université Paul Sabatier - ENFA , 31062 Toulouse Cedex 9 , France.
authors.forename: Boris
authors.initials: B
authors.lastname: Delahaie
authors.affiliation: INRA, UMR 1062 CBGP (INRA, IRD, Cirad, Montpellier SupAgro) , Campus de Baillarguet, 34988 Montferrier-sur-Lez , France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Gautier
authors.affiliation: INRA, GeT-PlaGe, Genotoul, 24 chemin de Borde Rouge, Auzeville, CS 52627, 31326 Castanet-Tolosan, France; INRA, UAR1209, 24 chemin de Borde Rouge, Auzeville, CS 52627, 31326 Castanet-Tolosan, France.
authors.forename: Emeline
authors.identifier: 0000-0003-2629-7773
authors.initials: E
authors.lastname: Lhuillier
authors.affiliation: Laboratoire Évolution et Diversité Biologique , UMR5174 CNRS, Université Paul Sabatier - ENFA , 31062 Toulouse Cedex 9 , France.
authors.forename: Pierre-Jean G
authors.initials: PG
authors.lastname: Malé
authors.affiliation: Laboratoire Évolution et Diversité Biologique , UMR5174 CNRS, Université Paul Sabatier - ENFA , 31062 Toulouse Cedex 9 , France.
authors.forename: Joris A M
authors.initials: JA
authors.lastname: Bertrand
authors.affiliation: Laboratoire Évolution et Diversité Biologique , UMR5174 CNRS, Université Paul Sabatier - ENFA , 31062 Toulouse Cedex 9 , France.
authors.forename: Josselin
authors.initials: J
authors.lastname: Cornuault
authors.affiliation: Department of Chemistry , Fujita Health University, School of Health Sciences , Toyoake Aichi 470-1192 , Japan.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Wakamatsu
authors.affiliation: INRA, GeT-PlaGe, Genotoul, 24 chemin de Borde Rouge, Auzeville, CS 52627, 31326 Castanet-Tolosan, France; GenPhySE, Université de Toulouse, INRA, INPT, INP-ENVT, 24 chemin de Borde Rouge, Auzeville, CS 52627, 31326 Castanet-Tolosan, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Bouchez
authors.affiliation: Laboratoire Évolution et Diversité Biologique , UMR5174 CNRS, Université Paul Sabatier - ENFA , 31062 Toulouse Cedex 9 , France.
authors.forename: Claire
authors.initials: C
authors.lastname: Mould
authors.affiliation: Laboratoire Évolution et Diversité Biologique , UMR5174 CNRS, Université Paul Sabatier - ENFA , 31062 Toulouse Cedex 9 , France.
authors.forename: Jade
authors.initials: J
authors.lastname: Bruxaux
authors.affiliation: Laboratoire Évolution et Diversité Biologique , UMR5174 CNRS, Université Paul Sabatier - ENFA , 31062 Toulouse Cedex 9 , France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Holota
authors.affiliation: National Museum of Natural Sciences , Spanish National Research Council (CSIC) , 28006 Madrid , Spain.
authors.forename: Borja
authors.initials: B
authors.lastname: Milá
authors.affiliation: Laboratoire Évolution et Diversité Biologique , UMR5174 CNRS, Université Paul Sabatier - ENFA , 31062 Toulouse Cedex 9 , France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Thébaud
keywords: Zosterops; chromosome 1; melanism; polymorphism; selective sweep