Meeting Abstract

7.2  Sunday, Jan. 4  Factors that Influence the Strength of Indirect Interactions Mediated by Phenotypic Plasticity MINER, BG*; MULLER, E; PORTER, S; MORGAN, SG; Western Washinton University; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis benjamin.miner@wwu.edu

For several decades ecologists have been interested in comparing the relative importance of direct and indirect interactions. In recent years, research has focused on comparing different types of indirect effects. This is especially the case for trophic cascades. The classic density-mediated or non-consumptive indirect effects are mediated through predators consuming and reducing prey population sizes. In contrast, trait-mediated or non-consumptive indirect effects are mediated through plasticity of prey in response to a predator. Which one is more important depends on the system, and thus the question becomes what aspects of a system determine the relative strength of these two types of interactions. We present the results from several laboratory experiments on an intertidal marine trophic cascade. A seastar is the predator (Pycnopodia helianthoides, or Pisaster ochraceus), a snail (Chlorostoma funebralis) is the prey, and algae (unidentified species of diatoms, or Macrocystis sp.) are the resource. We determined that the strength of non-consumptive effects is altered with cue concentration, and degradation of cue. Additionally, results suggest that prey condition and density also influence the strength of non-consumptive effects. These results have important implications for comparing the relative strengths of consumptive vs. non-consumptive indirect effects.