title: Adaptive divergence in flowering time among natural populations of Arabidopsis thaliana: Estimates of selection and QTL mapping.
abstract: To identify the ecological and genetic mechanisms of local adaptation requires estimating selection on traits, identifying their genetic basis, and evaluating whether divergence in adaptive traits is due to conditional neutrality or genetic trade-offs. To this end, we conducted field experiments for three years using recombinant inbred lines (RILs) derived from two ecotypes of Arabidopsis thaliana (Italy, Sweden), and at each parental site examined selection on flowering time and mapped quantitative trait loci (QTL). There was strong selection for early flowering in Italy, but weak selection in Sweden. Eleven distinct flowering time QTL were detected, and for each the Italian genotype caused earlier flowering. Twenty-seven candidate genes were identified, two of which (FLC and VIN3) appear under major flowering time QTL in Italy. Seven of eight QTL in Italy with narrow credible intervals colocalized with previously reported fitness QTL, in comparison to three of four in Sweden. The results demonstrate that the magnitude of selection on flowering time differs strikingly between our study populations, that the genetic basis of flowering time variation is multigenic with some QTL of large effect, and suggest that divergence in flowering time between ecotypes is due mainly to conditional neutrality.
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden.
authors.forename: Jon
authors.initials: J
authors.lastname: Ågren
authors.affiliation: Department of Plant Biology, Michigan State University, East Lansing, Michigan, 48824.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Oakley
authors.affiliation: Department of Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18 D, SE-752 36, Uppsala, Sweden.|WWF Norway, Postboks 6784, St. Olavs Plass, 0130, Oslo, Norway.
authors.forename: Sverre
authors.initials: S
authors.lastname: Lundemo
authors.affiliation: Department of Plant Biology and W. K. Kellogg Biological Station, Michigan State University, East Lansing, Michigan, 48824.
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Schemske
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D005075:Biological Evolution; D060146:Ecotype; D035264:Flowers / Q000254:growth & development; D007558:Italy; D040641:Quantitative Trait Loci; D012098:Reproduction; D012621:Seasons; D012641:Selection, Genetic; D013548:Sweden
keywords: Adaptation; Arabidopsis thaliana; phenology; recombinant inbred lines; selection; trade-off