title: Evolution of the Selfing Syndrome in Arabis alpina (Brassicaceae).
abstract: BACKGROUND
  The transition from cross-fertilisation (outcrossing) to self-fertilisation (selfing) frequently coincides with changes towards a floral morphology that optimises self-pollination, the selfing syndrome. Population genetic studies have reported the existence of both outcrossing and selfing populations in Arabis alpina (Brassicaceae), which is an emerging model species for studying the molecular basis of perenniality and local adaptation. It is unknown whether its selfing populations have evolved a selfing syndrome.
  
  
  METHODS
  Using macro-photography, microscopy and automated cell counting, we compared floral syndromes (size, herkogamy, pollen and ovule numbers) between three outcrossing populations from the Apuan Alps and three selfing populations from the Western and Central Alps (Maritime Alps and Dolomites). In addition, we genotyped the plants for 12 microsatellite loci to confirm previous measures of diversity and inbreeding coefficients based on allozymes, and performed Bayesian clustering.
  
  
  CONCLUSIONS
  Plants from the three selfing populations had markedly smaller flowers, less herkogamy and lower pollen production than plants from the three outcrossing populations, whereas pistil length and ovule number have remained constant. Compared to allozymes, microsatellite variation was higher, but revealed similar patterns of low diversity and high Fis in selfing populations. Bayesian clustering revealed two clusters. The first cluster contained the three outcrossing populations from the Apuan Alps, the second contained the three selfing populations from the Maritime Alps and Dolomites.
  
  
  CONCLUSIONS
  We conclude that in comparison to three outcrossing populations, three populations with high selfing rates are characterised by a flower morphology that is closer to the selfing syndrome. The presence of outcrossing and selfing floral syndromes within a single species will facilitate unravelling the genetic basis of the selfing syndrome, and addressing which selective forces drive its evolution.
authors.affiliation: Institute of Evolutionary Biology and Environmental studies, University of Zurich, Zurich, Switzerland.
authors.forename: Andrew
authors.initials: A
authors.lastname: Tedder
authors.affiliation: Ecology, Department of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: Samuel
authors.initials: S
authors.lastname: Carleial
authors.affiliation: Institute of Evolutionary Biology and Environmental studies, University of Zurich, Zurich, Switzerland.
authors.forename: Martyna
authors.initials: M
authors.lastname: Gołębiewska
authors.affiliation: Institut für Biochemie und Biologie, Universität Potsdam, Potsdam-Golm, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Kappel
authors.affiliation: Institute of Evolutionary Biology and Environmental studies, University of Zurich, Zurich, Switzerland.
authors.forename: Kentaro K
authors.initials: KK
authors.lastname: Shimizu
authors.affiliation: Ecology, Department of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Stift
mesh_terms: D031214:Arabis / Q000502:physiology*; D005075:Biological Evolution; D018515:Plant Leaves / Q000502:physiology*; D011058:Pollen / Q000502:physiology*