Servick, Stein V. , Soltis, Pamela S. , Soltis, Douglas E. .
Genetic Evidence for Recurrent Autopolyploid Formation of Galax urceolata (Diapensiaceae).
Polyploidy has long been recognized as a significant force in the evolution of plants. Genomic studies indicate there have been multiple whole-genome duplications throughout the evolutionary history of angiosperms, indicating the importance of polyploidy in angiosperm diversification. However, most research has focused on allopolyploidy and synthetic autopolyploids, leaving naturally occurring autopolyploids generally underinvestigated. Recent studies indicate that the prevalence of autopolyploid speciation has been largely underestimated. To improve our understanding of the role of polyploidy in evolution, studies on naturally occurring autopolyploids are therefore essential. We seek to broaden our understanding of autopolyploidy as an evolutionary force in natural populations through investigation of the genetic consequences of whole-genome duplication in Galax urceolata (Diapensiaceae), long considered the classic example of autopolyploidy. Galax urceolata comprises 2x, 3x, and 4x cytotypes (n = 6) that are morphologically and chemically nearly identical, suggesting an autopolyploid origin. We screened 1065 individuals from 71 populations for ploidy using flow cytometry. Cytotypes can be clearly differentiated by this method (p = 3.97 x10-152). Diploid, triploid, and tetraploid cytotypes comprise 59%, 7%, and 34% of the individuals, respectively. Eight microsatellite loci have been used to assess (1) whether G. urceolata meets the theoretical genetic expectations of an autotetraploid, (2) the genetic structure within and among populations, and (3) the number of independent tetraploid origins. Microsatellite data are consistent with genetic expectations; nearly all alleles are shared with putative diploid progenitor(s), and genotypes contain 1-4 alleles per locus, suggestive of autopolyploid origins. Calculations of genetic diversity indicate G. urceolata maintains clear genetic and geographic structure, with clusters of populations from the Piedmont and Coastal, North, South, and Appalachian regions of its distribution. Genetic data conservatively suggest a minimum of 10 independent tetraploid origins, although many more may exist.
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1 - University of Florida, Department of Botany, Florida Museum of Natural History, P.O. Box 117800, Gainesville, Florida, 32611-7800, USA
2 - University of Florida, Florida Museum of Natural History, Florida Museum of Natural History, P.O. Box 117800, Gainesville, FL, 32611-7800, USA
3 - University of Florida, Department of Biology, 220 Bartram Hall, P.O. Box 118526, Gainesville, Florida, 32611, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 553B/Convention Center
Date: Monday, August 2nd, 2010
Time: 3:45 PM