title: Cline coupling and uncoupling in a stickleback hybrid zone.
abstract: Strong ecological selection on a genetic locus can maintain allele frequency differences between populations in different environments, even in the face of hybridization. When alleles at divergent loci come into tight linkage disequilibrium, selection acts on them as a unit and can significantly reduce gene flow. For populations interbreeding across a hybrid zone, linkage disequilibria between loci can force clines to share the same slopes and centers. However, strong ecological selection on a locus can also pull its cline away from the others, reducing linkage disequilibrium and weakening the barrier to gene flow. We looked for this "cline uncoupling" effect in a hybrid zone between stream resident and anadromous sticklebacks at two genes known to be under divergent natural selection (Eda and ATP1a1) and five morphological traits that repeatedly evolve in freshwater stickleback. These clines were all steep and located together at the top of the estuary, such that we found no evidence for cline uncoupling. However, we did not observe the stepped shape normally associated with steep concordant clines. It thus remains possible that these clines cluster together because their individual selection regimes are identical, but this would be very surprising given their diverse roles in osmoregulation, body armor, and swimming performance.
authors.affiliation: Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada. vines@zoology.ubc.ca.|Axios Review Editorial Office, Vancouver, British Columbia, V5V 3X3, Canada. vines@zoology.ubc.ca.
authors.forename: Timothy H
authors.initials: TH
authors.lastname: Vines
authors.affiliation: Department of Biology, Saint Mary's University, Nova Scotia, B3H 3C3, Canada.
authors.forename: Anne C
authors.initials: AC
authors.lastname: Dalziel
authors.affiliation: Women's Health Research Institute, Vancouver, British Columbia, V6H 3N1, Canada.
authors.forename: Arianne Y K
authors.initials: AY
authors.lastname: Albert
authors.affiliation: Integrative Biology, University of Texas at Austin, Austin, Texas, 78712.
authors.forename: Thor
authors.initials: T
authors.lastname: Veen
authors.affiliation: Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Schulte
authors.affiliation: Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada.
authors.forename: Dolph
authors.initials: D
authors.lastname: Schluter
mesh_terms: D000818:Animals; D017753:Ecosystem; D005260:Female; D029941:Fish Proteins / Q000235:genetics*; D051456:Gene Flow; D015810:Linkage Disequilibrium; D008297:Male; D060047:Reproductive Isolation; D012641:Selection, Genetic; D023701:Smegmamorpha / Q000235:genetics*
chemical_list: D029941:Fish Proteins
keywords: Ectodysplasin; Gasterosteus aculeatus; hybridization; linkage disequibrium; reproductive isolation