Onagraceae as a model experimental system
Sytsma, Kenneth , Hahn, William , Williams, Cody , Karol, Kenneth .
Clarkia: a Californian chronicle of clades, clocks, chromosomes, and characters .
The largely Californian genus Clarkia (Onagraceae), although not the focus of Peter Raven's first scientific paper as a teenager, played a pivotal role in his early important scientific discoveries of plant speciation and chromosomal evolution. Clarkia has since become a model genus for studying evolutionary phenomena including determinants of species' range sizes, trait plasticity, fitness and adaptation, pollination biology, breeding systems, floral development, population genetics, aneuploidy and polyploidy, rapid speciation, and gene duplication and gene silencing. Despite its scientific importance, a molecular phylogenetic framework for the entire genus is lacking and thus the ability to fully appreciate these important evolutionary events has been hindered. We present here a nuclear and cpDNA based set of relationships for 39 of the 42 species of Clarkia representing all recognized sections and subsections in the genus. A small clade of three species (sects. Eucharidium and Clarkia) represents the sister to all other members of Clarkia. Although these trees are largely similar to the latest phylogenetic tree of Clarkia based on duplicated genes of nuclear pgi (but with more limited taxon sampling), there exists some strong discordance of species relationships between these results compared to those of pgi. Under Bayesian frameworks, geographical diversification in space and time, chromosome number and genome size evolution, and floral character state transitions were analyzed. BEAST analysis of a more inclusive clade of Onagraceae, permitting use of fossil calibrations, places the crown radiation of Clarkia around 10mya in the late Miocene. Rates of diversification within the genus are considerably greater within the last 2-3my. Diploid n=8,9 sections and their polyploid derivatives form a monophyletic group while the n=7 sections and their derivatives form a paraphyletic grade. The best supported hypothesis of genome evolution is one with two independent increases in size relative to the plesiomorphic condition.
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1 - University of Wisconsin-Madison, Department of Botany, 430 Lincoln Dr., Madison, WI, 53706, USA
2 - George Washington University, 37TH & O STREETS, WASHINGTON, DC, 20057, USA
4 - The New York Botanical Garden, 200 Street & Southern Boulevard, Bronx, NY, 10458, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Lenox Room/Chase Park Plaza
Date: Wednesday, July 13th, 2011
Time: 2:00 PM