Turning up the heat: temperature influences the relative importance of top-down and bottom-up effects.
Understanding how communities respond to changes in temperature is a major challenge for community ecology. Temperature influences the relative degree to which top-down and bottom-up forces structure ecological communities. In greenhouse experiments using the aquatic community found in pitcher plants (Sarracenia purpurea), I tested how temperature affected the relative importance of top-down (mosquito predation) and bottom-up (ant carcasses) forces on protozoa and bacteria populations. While bottom-up effects did not vary consistently with temperature, the top-down effects of predators on protozoa increased at higher temperatures. These results suggest that temperature could change the relative importance of top-down and bottom-up effects in ecological communities. Specifically, higher temperature may increase the strength of top-down effects by raising predator metabolic rate and concomitant processes (e.g., activity, foraging, digestion, growth) relative to cooler temperatures. These findings apply broadly to an understanding of trophic interactions in a variable environment and are especially relevant in the context of ongoing climate change.
Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA. dhoekman@wisc.edu
David
D
Hoekman
D000818:Animals; D001419:Bacteria; D009033:Culicidae / Q000502:physiology*; D004734:Energy Metabolism; D005247:Feeding Behavior; D020387:Food Chain; D006358:Hot Temperature; D007814:Larva / Q000502:physiology; D011156:Population Density; D052583:Sarraceniaceae / Q000502:physiology*