title: Population genetic variation, geographic structure, and multiple origins of autopolyploidy in Galax urceolata.
abstract: OBJECTIVE
  Whereas population genetic studies have examined allopolyploids, comparable studies of naturally occurring autopolyploids remain rare. To address fundamental questions regarding autopolyploidy, we undertook a detailed population genetic study of one of the classic examples of autopolyploidy, Galax urceolata (Diapensiaceae), which comprises diploid, triploid, and autotetraploid cytotypes. Galax is endemic to the Appalachian Mountains, the adjacent piedmont, sandhills, and coastal plain and represents perhaps the most widely known example of autopolyploidy in nature.
  
  
  METHODS
  Flow cytometry was used to diagnose ploidal level of ∼1000 individuals across 71 populations. We used 10 microsatellite markers to examine genetic variation across the geographic range of Galax and assessed multiple origins though comparisons of diploid, triploid, and tetraploid accessions using multiple analytical approaches.
  
  
  RESULTS
  Tetraploids had higher levels of heterozygosity than diploids did. Genetic variation in diploid and tetraploid Galax is geographically structured among the ecoregions of the southeastern United States. Autotetraploidy in Galax urceolata has occurred independently at least 46 times, with triploidy having occurred a minimum of 31 times.
  
  
  CONCLUSIONS
  Genetic differentiation among ecoregions suggests historical patterns of local adaptation. The numerous independent origins of tetraploid Galax reported here are among the highest frequencies of independent polyploidizations ever reported for any polyploid (auto- or allopolyploid).
authors.affiliation: Department of Biology, University of Florida, Gainesville, Florida 32611 USA.
authors.forename: Stein
authors.initials: S
authors.lastname: Servick
authors.affiliation: Department of Biology, University of Florida, Gainesville, Florida 32611 USA.
authors.forename: Clayton J
authors.initials: CJ
authors.lastname: Visger
authors.affiliation: Department of Biology, University of Florida, Gainesville, Florida 32611 USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Gitzendanner
authors.affiliation: Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611 USA Genetics Institute, University of Florida, Gainesville, Florida 32610 USA.
authors.forename: Pamela S
authors.initials: PS
authors.lastname: Soltis
authors.affiliation: Department of Biology, University of Florida, Gainesville, Florida 32611 USA.
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Soltis
mesh_terms: D001061:Appalachian Region; D001499:Bayes Theorem; D016000:Cluster Analysis; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D016013:Likelihood Functions; D019684:Magnoliopsida / Q000235:genetics*; D010802:Phylogeny; D011123:Polyploidy
keywords: Diapensiaceae; Galax urceolata; autopolyploidy; geographic structure; multiple polyploid origins; population genetics, southeastern United States