title: Naturally segregating loci exhibit epistasis for fitness.
abstract: The extent to which gene interaction or epistasis contributes to fitness variation within populations remains poorly understood, despite its importance to a myriad of evolutionary questions. Here, we report a multi-year field study estimating fitness of Mimulus guttatus genetic lines in which pairs of naturally segregating loci exist in an otherwise uniform background. An allele at QTL x5b-a locus originally mapped for its effect on flower size-positively affects survival if combined with one genotype at quantitative trait locus x10a (aa) but has negative effects when combined with the other genotypes (Aa and AA). The viability differences between genotypes parallel phenotypic differences for the time and node at which a plant flowers. Viability is negatively correlated with fecundity across genotypes, indicating antagonistic pleiotropy for fitness components. This trade-off reduces the genetic variance for total fitness relative to the individual fitness components and thus may serve to maintain variation. Additionally, we find that the effects of each locus and their interaction often vary with the environment.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA pmonnahan@ku.edu.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Monnahan
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA.
authors.forename: John K
authors.initials: JK
authors.lastname: Kelly
mesh_terms: D004843:Epistasis, Genetic; D005298:Fertility; D035264:Flowers / Q000033:anatomy & histology / Q000235:genetics; D056084:Genetic Fitness; D014644:Genetic Variation; D005838:Genotype; D032241:Mimulus / Q000033:anatomy & histology / Q000235:genetics*; D040641:Quantitative Trait Loci; D012641:Selection, Genetic
keywords: QTL; antagonistic pleiotropy; epistasis; field assay; fitness