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ESA Symposium: August 2007

Beyond single mechanisms: the relative and interactive importance of top-down and bottom-up mechanisms in plant invasions

Dana Blumenthal organized this symposium at the ESA meeting in San Jose in 2007. Cynthia (Cini) Brown served as co-organizer and moderator.  The house was packed, and the two panel discussions were excellent.  The abstract for the symposium follows:

Symposium Abstract: 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.


Event: Symposium

When: 08-August 2007

Where: San Jose, CA

Directions: Click here

Contact: Dana Blumenthal

Attendees/Speakers: Dana Blumenthal, Katriona Shea, Tim Seastedt, Jennifer Williams, Lorne Wolfe, John Wilson, John Parker, Andrew Norton

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