McAllister, Christine , Blaine, Russell , Kron, Paul , Bennett, Brent , Glotzbach, Anna , Kidson, Jennifer , Garrett, Heidi , Matzenbacher, Blanda , Miller, Allison .
Environmental Correlates of Cytotype Diversity in Big Bluestem (Andropogon gerardii).
Polyploidy has played a significant role in the diversification and evolution of plants. Polyploidization within plant lineages can lead to a mosaic of cytotypes across the range of a species, and the existence of multiple cytotypes within populations is well-documented in plants. However, the mechanisms by which this sometimes cryptic diversity is established and maintained are not always clear. Documenting the geographic distribution of cytotypes can be a critical first step in identifying whether abiotic factors are associated with whole genome duplication or habitat differentiation between cytotypes. Here, we examine patterns of cytotype diversity in big bluestem (Andropogon gerardii), the dominant species of the tallgrass prairie ecosystem. Because the physiology and population dynamics of A. gerardii drive tallgrass prairie ecosystem function (e.g. productivity, carbon sequestration), increasing our understanding of the patterns of cytotype diversity and the underlying drivers of these patterns will help clarify predictions of tallgrass prairie ecosystem responses to predicted climate change. Previous research has established the existence of multiple cytotypes within this species. The most common ploidy levels in A.gerardii are hexaploids (2n = 6x = 60) and enneaploids (2n = 9x = 90), with rare intermediate cytotypes (typically < 5% of sampled populations). The cytotypes are morphologically indistinguishable and occur in mixed ploidy populations in many parts of the range. We estimated ploidy level in 352 plants from 37 populations of A. gerardii in 18 states, using flow cytometry with silica-dried leaf samples. Fifteen populations (or 40.5%) showed evidence of mixed cytotypes. The population-level frequency of higher order polyploids (e.g. higher than 6x) ranged from 0% in the northern portion of the sampled range to 100% in the southern portions of the range. Mantel tests showed significant spatial autocorrelation of the higher ploidy levels. We tested for environmental correlates of cytotypic diversity using seven biologically relevant GIS-based climate layers selected from the 19 BIOCLIM layers (2.5 arc second resolution). A principal component analysis reduced these seven variables to two principal components that together explained 79.8% of the variation in the data. In order to account for spatial autocorrelation in the pattern of climate variation, we conducted partial Mantel tests on both principal components. These tests revealed that although most temperature-related variables were not significantly correlated with the frequency of higher ploidy levels in a population, high diurnal temperature range and low summer precipitation were significantly correlated with higher ploidy level.
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1 - Saint Louis University, Department of Biology, 3507 Laclede Avenue, St. Louis, MO, 63130, USA
2 - Southern Illinois University, Edwardsville, State Route 157, Edwardsville, IL, 62026, USA
3 - University of Guelph, Department of Botany, GUELPH, ON, N1G 2W1, Canada
4 - Principia College, Department of Biology and Natural Resources, 1 Maybeck Place, Principia College, Elsah, Illinois, 62028, United States
Presentation Type: Oral Paper:Papers for Sections
Location: Marlborough B/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 9:15 AM
Candidate for Awards:None