Wednesday, August 8, 2007: 1:30 PM-5:00 PM
A3&6, San Jose McEnery Convention Center
SYMP 15 - Beyond Single Mechanisms: The Relative and Interactive Importance of Bottom-up and Top-down Processes in Plant Invasion
To date, most work on mechanisms of plant invasion has focused on single mechanisms. However, to translate scientific understanding of invasion processes into strategies for preventing or controlling invasions it is necessary to understand which mechanisms are most important in which circumstances. This symposium will highlight current research that addresses multiple mechanisms of invasion, and attempt to gauge the predictive power of such approaches. The first half of the symposium will consist of experimental studies of individual invasive species that explicitly address the relative and interactive roles of bottom up and top-down factors. A short introduction will describe the symposium's goals and the relationship of these to the subsequent presentations. Then there will be an overview of relevant invasion mechanisms, and discussion of the overriding importance of competition to invasion of two Carduus species, and recently identified interactions between competition, herbivory, and dispersal. Then we will show that both herbivory and disturbance are important to another aster, Centaurea diffusa, and suggest that both healthy competitors and biological control are necessary to stem its spread. Building on this theme, we will then use cross-continental field studies and population models to demonstrate that while both herbivory and disturbance influence Cynoglossum officinale invasion, only herbivory can explain why it is more successful in its exotic than its native range. Finishing will be a discussion of the distinction between ecological and evolutionary processes, and the way each interacts with enemy release and disturbance to influence Silene latifolia invasion. The second half of the symposium will focus on multi-species approaches to the symposium topic and implications for invasive species management through biological control and ecological restoration. First, the relative importance of different mechanisms determining invasive plant distribution. then we will consider the relative importance of specialist and generalist herbivores, and raise the possibility that the restoration of patterns of herbivory may be key to invasive species control. We will show that among 260 European species, those with moderate to high N requirements lose the most enemies upon moving to N. America, and suggest that restoration that reduces resource availability may therefore reduce enemy release and inhibit exotic species. Finally, we will discuss the importance of bottom-up/top-down interactions to biological control, drawing on both existing literature and his own work with Linaria dalmatica.
Organizer:Dana Blumenthal, USDA-ARS
Co-organizer:Cynthia Brown, Colorado State University
Moderator:Cynthia Brown, Colorado State University
1:30 PMIntroduction
Dana Blumenthal, USDA-ARS
1:35 PMMultiple factors affect invasions: An overview and a case study
Katriona Shea, The Pennsylvania State University
1:55 PMAnalysis of top-down and bottom-up controls for diffuse and spotted knapweed (Centaurea spp) in North America
Tim Seastedt, University of Colorado, David G. Knochel, University of Colorado, Katharine N. Suding, University of California, Irvine
2:15 PMUsing experiments in the native and introduced ranges to understand exotic plant success
Jennifer L. Williams, University of Montana
2:35 PMA tale of two continents: The role of different evolutionary forces in life history shifts during biological invasions
Lorne Wolfe, Georgia Southern University
2:55 PMPanel Discussion
3:10 PMBreak
3:20 PMExplaining and predicting the range of introduced plants: Perspectives from South Africa
David Richardson, Center for Invasion Biology, John. R Wilson, Center for Invasion Biology, Şerban Procheş, Centre for Invasion Biology, Wilfried Thuiller, Université Joseph Fourier
3:40 PMRelative roles of generalist vs. specialist herbivores in plant invasions
John D. Parker, Cornell University, Robert L. Johnson, Cornell University, Anurag A. Agrawal, Cornell University
4:00 PMTesting the resource-enemy release hypothesis: Pathogen release and nitrogen availability in plant invasion
Dana Blumenthal, USDA-ARS, Charles Mitchell, University of North Carolina, Chapel Hill
4:20 PMResource availability and herbivore impact: Does herbivore behavior predict biological control efficacy?
Andrew Norton, Colorado State University
4:40 PMPanel Discussion

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See more of The ESA/SER Joint Meeting (August 5 -- August 10, 2007)