Majure, Lucas , Judd, Walter , Soltis, Pamela , Soltis, Douglas .
Searching for needles in a stack of needles: diploids in Opuntia s.s. and what they tell us about the evolutionary history of the clade.
The widespread American clade Opuntia s.s. is well known for consisting of a very high percentage of polyploid species. In general, polyploids are typically more widespread and apparently more successful than the geographically restricted and therefore less common diploids. We wanted to know 1) the geographical delineation of diploids and polyploids in a subclade of Opuntia s.s., the Humifusa clade, and 2) what the diploid phylogeny can tell us about the origin of the clade and polyploid taxa within the clade. We analyzed 15 taxa of the Humifusa clade with individuals sampled from across the United States, using cytological (including 250 new counts) and phylogenetic data (5 plastid and 2 nuclear loci) to answer these questions. Diploid species are confined to the southeastern United States and two locations in the southwestern United States. Our phylogenetic results suggest that the Humifusa clade originated in the southeastern United States and allopolyploid formation resulted from contact with divergent members of its own clade and possibly its sister clade (the Macrocentra clade), as the Humifusa clade spread north and west from the southeastern United States. Drastic fluctuations in sea level likely were a factor in the union of evolutionarily divergent species that led to the formation of polyploid taxa, since geographic boundaries of certain diploid and polyploid taxa follow the predictions of sea level changes during previous interglacial events of the late Miocene and Pleistocene epochs.
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1 - University Of Florida, Florida Museum Of Natural History, P.O. Box 117800, Gainesville, FL, 32611, USA
2 - University of Florida, Department of Biology, Po Box 118526, Gainesville, FL, 32611, USA
3 - University Of Florida, Florida Museum Of Natural History, PO BOX 117800, Gainesville, FL, 32611-7800, USA
4 - University of Florida, Department of Biology, Gainesville, FL, 32611, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lindell B/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 2:30 PM