J. Shoshana Rosenberg

THE IMPORTANCE OF HABITAT SELECTION AND POST-COLONIZATION PREDATION IN AQUATIC COMMUNITY ASSEMBLY. J. Shoshana Rosenberg¹, James Vonesh¹,Jonathan M. Chase¹, Biology Department, Washington University, St. Louis, MO¹.

Historically, the lethal effect of predators has been considered a key factor in determining the structure of aquatic communities. However, recent experiments have highlighted the importance of non-lethal predator effects on prey communities. For example, predators can cause many aquatic species (e.g., mosquitoes, diving beetles, midges, frogs) to alter patterns of habitat selection. These findings raise the possibility that predator effects on habitat selection also contribute to aquatic community composition. In this experiment, we examine the relative importance of habitat selection and predation in the assembly of aquatic communities. To test for predator-induced changes in habitat selection, we put caged fish into half of 24 colonization pools, creating predator cues to which colonizing species could respond while eliminating predation as a contributing factor in community assembly. Every 3 to 4 days, we identified and counted every organism that colonized each of the 24 pools to determine colonization differences between pools with and without predator cues. We then transferred all organisms from each colonization pool to a corresponding focal pool either with or without predation (lethal, uncaged fish). At the end of 4 weeks, we compared differences between the resulting communities to determine the importance of habitat selection in aquatic community assembly. We found that habitat selection alters the final abundance of some (but not all) individual taxa, as well as the total community abundance. Habitat selection does not appear to affect community richness (number of taxa in the community) or primary productivity. In general, aquatic predation seems to have the greatest effect, but habitat selection also plays an important role in aquatic community assembly.