title: Mating system divergence affects the distribution of sequence diversity within and among populations of recently diverged subspecies of Clarkia xantiana (Onagraceae).
abstract: OBJECTIVE
  The population biology of outcrossing and self-fertilizing taxa is thought to differ because of the advantage that selfers have in colonizing unoccupied sites where mates and pollinators may be limiting (Baker's Law). This reduced tendency for outcrossers to colonize new sites, along with their greater dependence on pollinators to disperse pollen, has the potential to differently influence the genetic diversity and structure of outcrossing and selfing populations.
  
  
  METHODS
  We conducted a comparative population genetic study of two sister outcrossing and selfing subspecies of Clarkia xantiana that have very recently diverged. We used DNA sequence variation (>40 kb from eight nuclear loci) from large samples of individuals from 14 populations to assess geographic patterns of genetic diversity and make inferences about the demographic and colonization histories of each subspecies.
  
  
  RESULTS
  We show that sequence variation is strongly reduced across all selfing populations. The demographic history of selfing populations exhibits recent colonization bottlenecks, whereas such bottlenecks are rarely observed for the outcrosser. The greater effect of genetic drift in the selfer has resulted in strong population genetic structure, but with no pattern of isolation by distance. By contrast, the stronger effect of gene flow in the outcrosser has resulted in considerably less structure, but a significant pattern of isolation by distance.
  
  
  CONCLUSIONS
  Taken together, our results suggest that selfing populations are not at migration-drift equilibrium, are affected by strong episodes of genetic drift during colonization, and experience little or no subsequent gene flow from other populations after those founder events.
authors.affiliation: Department of Plant Biology, 1445 Gortner Avenue, University of Minnesota, Saint Paul, Minnesota 55108 USA moeller@umn.edu.
authors.forename: James B
authors.initials: JB
authors.lastname: Pettengill
authors.affiliation: Department of Plant Biology, 1445 Gortner Avenue, University of Minnesota, Saint Paul, Minnesota 55108 USA.
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Briscoe Runquist
authors.affiliation: Department of Plant Biology, 1445 Gortner Avenue, University of Minnesota, Saint Paul, Minnesota 55108 USA moeller@umn.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Moeller
mesh_terms: D002140:California; D031663:Clarkia / Q000235:genetics* / Q000502:physiology; D018744:DNA, Plant; D014644:Genetic Variation; D012098:Reproduction; D057945:Self-Fertilization; D017422:Sequence Analysis, DNA
chemical_list: D018744:DNA, Plant
keywords: Baker’s law; breeding system; colonization bottleneck; demographic history; dispersal; floral evolution; isolation by distance; mating system; self-fertilization; single nucleotide polymorphism