| Abstract Detail
Paleobotany Brightly, William [1], Stromberg, Caroline A. E. [2], Osborne, Colin [3], Hartley, Sue [4]. Exploring the Adaptive Role of Biogenic Silica in Poaceae, a Phylogenetic Approach. The deposition of biogenic silica in tissues, mainly in the form of solid phytoliths, is widespread among vascular plants. This deposition is controlled by both genetic and environmental factors (e.g., rates of evapotranspiration), resulting in variable gross silica concentrations among taxa and individual plants. The role of silica is especially well studied in the grass family (Poaceae), because of its economical and ecological importance, and because of the relatively high biosilica concentrations of many grasses. Several biological functions for grass phytoliths have been proposed, including mechanical support and drought resistance. In particular, much research has focused on the role of phytoliths as herbivore defense. A longstanding idea within the field of Paleontology holds that open habitat grasses, particularly C4 grasses (which came to dominate grass communities at low-mid latitudes), evolved increasingly higher concentrations of phytoliths as large, mammalian grazers diversified during the Neogene. This, along with empirical observations, has lead to the general hypothesis that C4 grasses possess higher biosilica concentrations than C3 grasses. However, tests of this hypothesis have yielded contradictory results, in large part because these studies have not adequately accounted for phenotypic plasticity (i.e., by comparing grasses that may have experienced different levels of evapotranspiration). Here we test the hypothesis that C4 grasses produce higher concentrations of phytoliths than C3 grasses using material collected from individuals grown under the same environmental conditions, thus controlling for the potentially confounding effects of environmental variation. Material from 248 species of Poaceae was collected from the University of Sheffield and sampled for both phytolith extraction and silica concentration analysis. Silica concentration data were collected for a total of 133 species using a portable X-ray fluorescence spectrometer, at the University of York. Phylogenetic generalized least squares analysis was then used to explore the relationship between silica concentration and photosynthetic pathway. Preliminary results suggest that there is no significant difference in biogenic silica accumulation between C3 and C4 grasses, calling into question the idea that the diversification and dominance of large, grazing mammals selected for higher silica concentrations across C4 grasses. Future analyses will further explore this hypothesis by investigating the relationship between silica concentration and habitat openness, ecological dominance (in both C3 and C4 species), and herbivore pressure more directly. Examination of the phytolith assemblages of the species investigated herein will also be used to test for phylogenetic patterns in silica allocation among open-habitat grasses.
Log in to add this item to your schedule
1 - University of Washington, 24 Kincaid Hall, Box 351800, Seattle, WA, 98195-1800, United States
2 - University Of Washington, Department of Biology, 24 Kincaid Hall, Box 351800, Seattle, Washington, 98195-1800, United States
3 - University of Sheffield, Department of Animal and Plant Sciences, Alfred Denny Building, Western Bank, Sheffield, S10 2TN, UK
4 - University of York, Biology, Wentworth Way, York, YO10 5DD, UK
Keywords:
phytolith
silica
herbivore defense
grass.
Presentation Type: Oral Paper
Session: 28, Mesozoic to Pleistocene Paleobotany
Location: 102/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 4:45 PM
Number: 28013
Abstract ID:901
Candidate for Awards:None |
