Document: JON-3-52-3

Interactive effects of dispersal and predation on pond zooplankton communities .

SHURIN, J.B.*

University of Chicago, Chicago, IL ¹

Abstract:
Theory suggests that predators can have variable effects on prey species composition, diversity, and trophic structure at local and regional scales. The consequences of invasion or extinction of a predator may depend on the traits of species in the regional pool and their rates of dispersal among habitats. I tested the effects of introduction of fish and insect predators on experimental zooplankton communities that were either connected to or isolated from the regional species pool. Predators had negative effects on local zooplankton diversity in the absence of dispersal and positive effects when immigration was allowed. Fish facilitated invasion by species that were excluded in their absence. The effects of predators on zooplankton size structure and phytoplankton biomass were independent of the dispersal treatment. Invasion by species from the region compensated for the loss of species diversity due to predation, but not for the ecosystem functions performed by those species. The results suggest that predators promote regional diversity and have variable effects on local diversity depending on how quickly ponds approach biogeographic equilibrium with respect to the regional species pool.

Keywords: biogeograhy, spatial dynamics, food webs

This abstract is being presented at: 8:15 AM in session:
Oral Session #37: Phytoplankton.