title: Plumage Genes and Little Else Distinguish the Genomes of Hybridizing Warblers.
abstract: When related taxa hybridize extensively, their genomes may become increasingly homogenized over time. This mixing via hybridization creates conservation challenges when it reduces genetic or phenotypic diversity and when it endangers previously distinct species via genetic swamping [1]. However, hybridization also facilitates admixture mapping of traits that distinguish each species and the associated genes that maintain distinctiveness despite ongoing gene flow [2]. We address these dual aspects of hybridization in the golden-winged/blue-winged warbler complex, two phenotypically divergent warblers that are indistinguishable using traditional molecular markers and that draw substantial conservation attention [3-5]. Whole-genome comparisons show that differentiation is extremely low: only six small genomic regions exhibit strong differences. Four of these divergence peaks occur in proximity to genes known to be involved in feather development or pigmentation: agouti signaling protein (ASIP), follistatin (FST), ecodysplasin (EDA), wingless-related integration site (Wnt), and beta-carotene oxygenase 2 (BCO2). Throat coloration-the most striking plumage difference between these warblers-is perfectly associated with the promoter region of agouti, and genotypes at this locus obey simple Mendelian recessive inheritance of the black-throated phenotype characteristic of golden-winged warblers. The more general pattern of genomic similarity between these warblers likely results from a protracted period of hybridization, contradicting the broadly accepted hypothesis that admixture results from solely anthropogenic habitat change in the past two centuries [4]. Considered in concert, these results are relevant to both the genetic architecture of avian feather pigmentation and the evolutionary history and conservation challenges associated with these declining songbirds.
authors.affiliation: Fuller Evolutionary Biology Program, Cornell Lab of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA; Department of Ecology and Evolutionary Biology, Cornell University, Corson Hall, Ithaca, NY 14853, USA. Electronic address: toews@cornell.edu.
authors.forename: David P L
authors.initials: DP
authors.lastname: Toews
authors.affiliation: Fuller Evolutionary Biology Program, Cornell Lab of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA; Department of Ecology and Evolutionary Biology, Cornell University, Corson Hall, Ithaca, NY 14853, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Taylor
authors.affiliation: Canadian Wildlife Service, Environment and Climate Change Canada, 351 St. Joseph Boulevard, Gatineau, Québec K1A 0H3, Canada.
authors.forename: Rachel
authors.initials: R
authors.lastname: Vallender
authors.affiliation: Department of Evolution, Ecology and Organismal Biology, University of California, Riverside, Batchelor Hall, Riverside, CA 92521, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Brelsford
authors.affiliation: Fuller Evolutionary Biology Program, Cornell Lab of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA.
authors.forename: Bronwyn G
authors.initials: BG
authors.lastname: Butcher
authors.affiliation: Department of Biological Statistics and Computational Biology, Cornell University, Weill Hall, Ithaca, NY 14853, USA.
authors.forename: Philipp W
authors.initials: PW
authors.lastname: Messer
authors.affiliation: Fuller Evolutionary Biology Program, Cornell Lab of Ornithology, Cornell University, 159 Sapsucker Woods Road, Ithaca, NY 14850, USA; Department of Ecology and Evolutionary Biology, Cornell University, Corson Hall, Ithaca, NY 14853, USA.
authors.forename: Irby J
authors.initials: IJ
authors.lastname: Lovette
mesh_terms: D000818:Animals; D030161:Avian Proteins / Q000235:genetics* / Q000378:metabolism; D005075:Biological Evolution; D003247:Conservation of Natural Resources; D005241:Feathers / Q000502:physiology; D016678:Genome; D006824:Hybridization, Genetic; D010641:Phenotype; D010858:Pigmentation; D020641:Polymorphism, Single Nucleotide; D020308:Songbirds / Q000235:genetics*
chemical_list: D030161:Avian Proteins