McAllister, Chrissy , Kron, Paul , Blaine, Russell , Miller, Allison .
Environmental Determinants of Cytotype Diversity in Big Bluestem (Andropogon gerardii).
Polyploidy, or whole genome duplication, played a significant role in the diversification and evolution of plants. The existence of multiple cytotypes (individuals of differing ploidy level) within populations is well-documented in plants, but the mechanisms by which this diversity is created and/or maintained are not always clear. An understanding of the geographic distribution of cytotypes can provide a framework for investigating niche separation as a possible driver of cytotype diversity across a species' range. Here, we investigate patterns of cytotype diversity in big bluestem (Andropogon gerardii), the dominant species of the tallgrass prairie ecosystem, from 29 localities across the core of the native range of the species. Because A. gerardii physiology and population dynamics play a significant role in tallgrass prairie ecosystem function (e.g. productivity, carbon sequestration), advancing understanding of patterns of cytotype diversity and their possible drivers is crucial for clarifying predictions of how the tallgrass prairie ecosystem will respond to expected climate change. Populations of A. gerardii typically contain two cytotypes - hexaploids (2n = 6x = 60) and enneaploids (2n = 9x = 90), which are morphologically indistinguishable in the field. We estimated ploidy level in approximately 10 plants per population from 18 localities, using a protocol for flow cytometry with field-collected, silica-dried leaf material. This data was combined with previously published ploidy values from leaf samples collected from populations in 11 additional localities in 1990. Using DIVA-GIS, we extracted thirty-year monthly precipitation and temperature averages as well as the 19 bioclimatic variables from BIOCLIM for all localities. A principal components analysis (PCA) of these variables was used to identify uncorrelated PCs. Three principal components (PC1, PC2, and PC3) accounted for 92.2% of the variation in climate variables. Principal component 1 accounted for 78.0% of the total variation among localities, PC2 accounted for 7.7% and PC3 accounted for 6.6%. Most precipitation and temperature variables loaded heavily onto PC1, with the exception of precipitation in July and August (loading onto PC2) and precipitation in June (loading onto PC3). A significant logistic regression (p = 0.001) indicated the ability of PC2 in to predict localities' memberships in one of the two ploidy level classifications (<10 9x="" cytotype="" and="">10% 9x cytotype). This implies that summer precipitation may be a driving factor in the maintenance of 9x cytotypes in a population.
Log in to add this item to your schedule
1 - Saint Louis University, Biology, 3507 Laclede Ave, St. Louis, MO, 63103, USA
2 - University of Guelph, Department of Integrative Biology, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada
3 - Maryville University, Department of Sciences, 650 Maryville University Drive, St. Louis, MO, 63141, USA
4 - Saint Louis University, Department of Biology, 3507 Laclede Avenue, St. Louis, MO, 63103, USA
Presentation Type: Poster:Posters for Sections
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM