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Harvard Forest Symposium Abstract 2013

  • Title: Oak dispersal: An integrative approach (an overview of activities by Bullard Fellow, M. Steele)
  • Primary Author: Michael Steele (Wilkes University)
  • Abstract:

    My research over the past two decades has focused on the interactions between oaks (Quercus spp.) and their seed predators and dispersers and the resulting implications for understanding the process of oak dispersal. These studies, which include research throughout the U.S., central Mexico, Costa Rica, and, most recently, several areas of China, examine how the physical and chemical characteristics of acorns influence the behavioral decisions of scatter-hoarding rodents and jays and, in turn, the dispersal and establishment of the oaks. My research has included studies on (1) tri-trophic interactions between weevils, rodents and oaks, (2) selective consumption of weevil-infested acorns and dispersal and caching of sound acorns, (3) the influence of chemical gradients and seed size on partial damage of acorns and their subsequent germination and establishment, (4) selective dispersal of acorns of the red oak group (RO, section Lobatae) over those of white oaks (WO, section Quercus) due to the delayed germination and reduced perishability of ROs, (5) the innate basis of embryo excision of WO acorns by gray squirrels and its implications for dispersal and establishment of WOs, (6) the ability of tree squirrels to detect seed dormancy based on olfactory cues in the pericarp of acorns, (7) effects of forest seed composition on differential patterns of dispersal in RO, WO and American chestnut, (8) cache management by rodents including cache recovery and re-caching behavior, and (9) effects of forest fragmentation on seed dispersal by blue jays.

    As a Bullard Fellow, my goals are four fold. First, I am devoting a portion of my time to initiating a book on oak dispersal tentatively entitled, The Oak Dispersal Syndrome: A Study in Plant-Animal Interactions. My goals with this volume are to synthesize my research in a way that contributes to a better understanding of both the specific process of animal-mediated seed dispersal, and to contribute to a more unified theory of seed dispersal in general. In addition, I hope to contribute to a better global understanding of oak dispersal and its implications for the conservation of threatened oak forests. Second, I have begun studies here with E. Crone and D. Orwig to examine growth and reproductive trade-offs in three species of oaks based on 13 years of acorn production at three PA sites. E. Crone and I are also examining the relationship between acorn production and weevil seed predation, and comparing the masting patterns of RO and WO species as it relates to dispersal trajectories. Third, I am using a portion of my time to forge a new long-term avenue of research on global/biogeographic patterns of oak-animal interactions and oak ecology. To do this, I seek to build a team of collaborators from China and the U.S. (Purdue, W& M, VCU, Harvard) to evaluate acorn-animal interactions across gradients of latitude and elevation. The study will compare patterns of insect (e.g. Curculio spp.) damage, acorn chemistry (i.e., protein, lipid, carbohydrate, tannin, and key minerals), acorn size and other physical characteristics, patterns of seed damage, and the ability of acorns to withstand insect and rodent damage across gradients in both NA and China. Finally, I have devoted considerable time during this fellowship towards completing several manuscripts related to acorn-rodent interactions, scatter hoarding strategies by rodents and jays, rodent seed dispersal, and effects of forest seed composition on acorn dispersal patterns.

  • Research Category: Biodiversity Studies