Stein Servick1, Clayton J Visger1, Matthew A Gitzendanner1, Pamela S Soltis2, Douglas E Soltis1. 1. Department of Biology, University of Florida, Gainesville, Florida 32611 USA. 2. Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611 USA Genetics Institute, University of Florida, Gainesville, Florida 32610 USA.
Abstract
PREMISE OF THE STUDY: 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. KEY 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).
PREMISE OF THE STUDY: 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. KEY 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).
Keywords:
Diapensiaceae; Galax urceolata; autopolyploidy; geographic structure; multiple polyploid origins; population genetics, southeastern United States
Authors: Juan Viruel; María Conejero; Oriane Hidalgo; Lisa Pokorny; Robyn F Powell; Félix Forest; Michael B Kantar; Marybel Soto Gomez; Sean W Graham; Barbara Gravendeel; Paul Wilkin; Ilia J Leitch Journal: Front Plant Sci Date: 2019-07-24 Impact factor: 5.753