PARENT SESSION
Oral Session # 5: Biogeography I: Community Structure and Diversity.
Presiding: B Enquist
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 104.
Spatial storage effect moderates species interactions in diverse ecosystems.
Sears, Anna*,1, Chesson, Peter1, 1 University of California, Davis, CA
ABSTRACT- While many researchers have studied variation in plant competition intensity along environmental gradients, it has previously been difficult to quantify how environmental variation impacts plant population and community dynamics. Spatial storage effect theory provides a set of tools to explain how patchiness or gradients in the environment, combined with species-specific differences in density dependence under different environmental conditions, can affect population persistence and the maintenance of species diversity. Using data from a variety of previously published neighborhood plant competition studies, we show that positive covariance between plant response to the environment and competition [Cov(E,C)], a key component of the spatial storage effect, is widespread in diverse ecosystems. This covariance, which is only found in the presence of environmental variation and at higher spatial scales, acts to increase population-level intraspecific competitive effects. Theory predicts that when Cov(E,C) is found for high-density, but not low-density species, it promotes species diversity. We found, for the response variables tested, Cov(E,C) was not always closely correlated with species density, which implies that in some of these systems, spatial variation may promote competitive exclusion. Cov(E,C) was also found to increase net population-level intraspecific competition intensity in systems where experiments showed a net positive effect of neighbors (facilitation) at local spatial scales. The methods developed for this study use new statistical techniques to extract previously inaccessible information from conventional experimental designs. Spatial storage effect theory appears to provide a promising context for studying a wide variety of metacommunity types and processes, and gives a depth of mechanistic understanding that was not possible using previous techniques.
Key words: facilitation, environmental gradients, neighborhood competition, spatial storage effect