title: Borrowed alleles and convergence in serpentine adaptation.
abstract: Serpentine barrens represent extreme hazards for plant colonists. These sites are characterized by high porosity leading to drought, lack of essential mineral nutrients, and phytotoxic levels of metals. Nevertheless, nature forged populations adapted to these challenges. Here, we use a population-based evolutionary genomic approach coupled with elemental profiling to assess how autotetraploid Arabidopsis arenosa adapted to a multichallenge serpentine habitat in the Austrian Alps. We first demonstrate that serpentine-adapted plants exhibit dramatically altered elemental accumulation levels in common conditions, and then resequence 24 autotetraploid individuals from three populations to perform a genome scan. We find evidence for highly localized selective sweeps that point to a polygenic, multitrait basis for serpentine adaptation. Comparing our results to a previous study of independent serpentine colonizations in the closely related diploid Arabidopsis lyrata in the United Kingdom and United States, we find the highest levels of differentiation in 11 of the same loci, providing candidate alleles for mediating convergent evolution. This overlap between independent colonizations in different species suggests that a limited number of evolutionary strategies are suited to overcome the multiple challenges of serpentine adaptation. Interestingly, we detect footprints of selection in A. arenosa in the context of substantial gene flow from nearby off-serpentine populations of A. arenosa, as well as from A. lyrata In several cases, quantitative tests of introgression indicate that some alleles exhibiting strong selective sweep signatures appear to have been introgressed from A. lyrata This finding suggests that migrant alleles may have facilitated adaptation of A. arenosa to this multihazard environment.
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138; Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA 02115;
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Arnold
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907;
authors.forename: Brett
authors.initials: B
authors.lastname: Lahner
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138;
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: DaCosta
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138;
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Weisman
authors.affiliation: Department of Ecology and Evolution, Stony Brook University, Stony Brook, NY 11794-5245;
authors.forename: Jesse D
authors.initials: JD
authors.lastname: Hollister
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907; Institute of Biological and Environmental Science, University of Aberdeen, Aberdeen, Scotland AB24 3UU, United Kingdom;
authors.forename: David E
authors.initials: DE
authors.lastname: Salt
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138; Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, United Kingdom.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Bomblies
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138; Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, United Kingdom levi.yant@jic.ac.uk.
authors.forename: Levi
authors.initials: L
authors.lastname: Yant
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000483:Alleles; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology*; D035264:Flowers / Q000502:physiology; D018745:Genome, Plant; D012987:Soil
chemical_list: D012987:Soil
keywords: adaptation; gene flow; plant; population genomics