PARENT SESSION
Symposium 24: Bridging the gap between theory and empiricism in ecology
Organized by: P Amarasekare and M Neubert
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 517 C, Level 5, Palais des congrès de Montréal
Stoichiometry and the spatial dynamics of consumer-resource coinvasions at Mount St. Helens.
Fagan, William*,1, Lewis, Mark2, Neubert, Michael2, Aumann, Craig 1, Apple, Jenny 3, Bishop, John3, 1 University of Maryland, College Park2 University of Alberta, Edmonton3 Woods Hole Oceanographic Institute, Woods Hole
ABSTRACT- I will report on the spatial dynamics of a co-invading consumer-resource pair. My colleagues and I developed a theoretical model with extensive empirical data from a long-studied field system in which native herbivorous insects attack a population of lupine plants recolonizing the primary successional landscape created by the 1980 volcanic eruption of Mount St. Helens. Using detailed data on the life history and interaction strengths of the lupine (Lupinus lepidus)and one of its herbivores (the gelechiid moth Filatima sp.), we develop a system of integrodifference equations to study plant-herbivore invasion dynamics. Our analyses yield several new insights into the spatial dynamics of co-invasions. In particular, we demonstrate that aspects of plant population growth and the intensity of herbivory under low-density conditions can determine whether the plant population spreads across a landscape or is prevented from doing so by the herbivore. In addition, we characterize the existence of threshold levels of spatial extent and/or temporal advantage for the plant that together define critical values of "invasion momentum," beyond which herbivores are unable to reverse a plant invasion. These thresholds have important implications for successional dynamics and the use of biological control agents to limit the spread of pest species.
Key words: invasion dynamics, inverse density dependence, plant-herbivore interactions, ecological stoichiometry