PARENT SESSION
Symposium 21: Miniature Worlds? Natural Microcosms as Model Ecological Systems
Organized by: D Srivastava and J Kolasa
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Chatham Ballroom C.
Stability of pitcher-plant microfaunal populations depends on food web structure.
Trzcinski, Kurtis*,1, Walde, Sandra1, Taylor, Phillip2, 1 Dalhousie University, Halifax, Nova Scotia, Canada2 Atlantic Cooperative Wildlife Ecology Research Network, Wolfville, Nova Scotia, Canada
ABSTRACT- Ecological theory suggests that top-down and bottom-up effects can be either stabilizing or destabilizing, depending on community structure. In this study we examined how food web structure affected the dynamics of three microfaunal taxa living in pitcher plants. We manipulated predator and resource levels and censused population in 60 communities that were open to colonization by microfauna and arthropods. Predation tended to decrease microfaunal abundances and to be destabilizing, leading to higher temporal variability and lower persistence times. Bottom-up effects varied with taxon, and depended on the manner in which resource availability was increased. Rotifer populations tended to be destabilized by the addition of resources under low predation and stabilized under high predation levels. Bottom-up effects were stabilizing for microflagellate populations, but this consumer responded, not directly to the addition of resources, but to the presence of midges whose activity increased bacterial abundances. We conclude that top-down effects tend to be destabilizing, but that the way bottom-up factors influence population dynamics within pitcher plant food webs depends on community structure, which in turn, depends mostly on patterns of colonization.
Key words: bottom-up, top-down, community assembly, population persistence