Kistenmacher, Michael , Gibson, J. Phil .
Pre-dispersal selection pressure of a specialized herbivore on the heteromorphic fruits of Grindelia ciliata (Asteraceae).
Seedling emergence is one of the most vulnerable life stages for many plants; therefore the timing and magnitude of emergence events are under strong selection pressures. Synchronous emergence of a filial generation may be selected against by biotic, abiotic or a combination of environmental factors. A leading hypothesis states that a strategy to offset the risks of germination due to environmental uncertainty is by producing heteromorphic fruits that have different germination requirements and dormancy states. In this study we investigated the natural seedling emergence of tri-morphic Grindeliaciliata (Asteraceae) fruits over the time course of one and a half years.Additionally, we investigated the feeding preference of a specialized seed herbivore among the three fruit types using cafeteria experiments. We found that seedling emergence occurs mainly in the fall for all fruit types although ray and intermediate fruits function to establish a one-year seed bank. Interestingly,the herbivore preferably consumed disc fruits, which represent majority of the first year's germination fraction. We can conclude that germination heteromorphism offsets the risks associated with germination but in doing so a fraction of the reproductive output becomes highly susceptible to herbivory.
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1 - University Of Oklahoma, Botany And Microbiology, George Lynn Cross Hall, 770 Van Vleet Oval, Norman, OK, 73019, USA
2 - University of Oklahoma, Department of Botany & Microbiology, 770 Van Vleet Oval, Norman, OK, 73019, USA
Predispersal seed predation.
Presentation Type: Oral Paper:Papers for Sections
Location: Franklin B/Hyatt
Date: Wednesday, July 11th, 2012
Time: 10:15 AM