title: Maintenance of a genetic polymorphism with disruptive natural selection in stickleback.
abstract: The role of natural selection in the maintenance of genetic variation in wild populations remains a major problem in evolution. The influence of disruptive natural selection on genetic variation is especially interesting because it might lead to the evolution of assortative mating or dominance [1, 2]. In theory, variation can persist at a gene under disruptive natural selection, but the process is little studied and there are few examples [3, 4]. We report a stable polymorphism in the bony armor of threespine stickleback maintained with a deficit of heterozygotes at the major underlying gene, Ectodysplasin (Eda) [5]. The deficit vanishes at the embryo life stage only to re-emerge in adults, indicating that disruptive natural selection, rather than nonrandom mating, is the cause. The mechanism enabling long-term persistence of the polymorphism is unknown, but disruptive selection is predicted to be frequency dependent, favoring homozygous genotypes when they become rare. Further research on the ecological and evolutionary processes affecting individual genes will ultimately lead to a better understanding of the causes of genetic variation in populations.
authors.affiliation: Biodiversity Research Centre and Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
authors.forename: Kerry B
authors.initials: KB
authors.lastname: Marchinko
authors.affiliation: Department of Aquatic Ecology, EAWAG, 79 Seestraße, 6047 Kastanienbaum, Switzerland.
authors.forename: Blake
authors.initials: B
authors.lastname: Matthews
authors.affiliation: Human Biology and Basic Sciences Divisions, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Arnegard
authors.affiliation: Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.
authors.forename: Sean M
authors.initials: SM
authors.lastname: Rogers
authors.affiliation: Biodiversity Research Centre and Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada. Electronic address: schluter@zoology.ubc.ca.
authors.forename: Dolph
authors.initials: D
authors.lastname: Schluter
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D005075:Biological Evolution; D001955:British Columbia; D053331:Ectodysplasins / Q000235:genetics* / Q000378:metabolism; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism; D060106:Lakes; D011110:Polymorphism, Genetic; D012641:Selection, Genetic; D023701:Smegmamorpha / Q000235:genetics*
chemical_list: D053331:Ectodysplasins; D029941:Fish Proteins