Top-down and bottom-up effects in a detrital food web: The pitcher plant inquiline community as a model food web | Posted on:2009-07-15 | Degree:Ph.D | Type:Dissertation | University:University of Notre Dame | Candidate:Hoekman, David | Full Text:PDF | GTID:1449390002498302 | Subject:Ecology | Abstract/Summary: | | Ecologists have long been interested in understanding factors that regulate food web dynamics. Both top-down and bottom-up forces affect populations within a food web, and their relative importance is influenced by many factors. Using the aquatic inquiline community found in pitcher plants as a model system, I conducted a series of field and laboratory experiments to explore various factors that influence the relative importance of top-down and bottom-up effects. Specifically, I examined the influence of (1) latitude (2) detritus processing and (3) temperature. I manipulated predator and resource density in factorial experiments and crossed these treatments with the three factors listed above. I measured the response of bacteria, protozoa and rotifers, the intermediate consumers in the food web.;I also examined the effect of detritus processing on the relative importance of top-down and bottom-up effects (chapter 4). Detritus processing did bolster bottom-up effects and surprisingly also resulted in some top-down effects, depending on the habitat preference of protozoa and rotifers. This demonstrated that detritus processors can also be important consumers in detritus-based food webs.;I first demonstrated that strong top-down and bottom-up effects are present in the pitcher plant food web and comparison with another study suggested that these effects varied with latitude (chapter 2). To pursue the latitudinal effect (chapter 3), I conducted two field experiments at disparate sites (Michigan and Florida). Differences in top-down and bottom-up effects were detected both within and among trophic levels and temperature was hypothesized as an important difference between the sites. I isolated the effect of temperature by manipulating top-down and bottomup effects at 6 different temperatures in a laboratory experiment (chapter 5). Temperature was hypothesized to increase both top-down and bottom-up effects and to potentially alter their relative importance. Higher temperature resulted in faster predator metabolism and consequently an increase in the magnitude of top-down effects. This suggests that temperature may be an important regulator of top-down effects and that climate change can have major effects on biological communities. | Keywords/Search Tags: | Top-down, Effects, Food web, Temperature, Pitcher, Relative importance, Factors | | Related items |
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