PARENT SESSION
Contributed Oral Session 74: Biodiversity: Aquatic Systems
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 513 C, Level 5, Palais des congrès de Montréal
Cascading diversity effects of omnivorous and carnivorous predators on plant diversity and biomass.
O'Connor, Mary*,1, Bruno, John2, 1 University of North Carolina - Chapel Hill, Chapel Hill, North Carolina2 University of North Carolina - Chapel Hill, Chapel Hill, North Carolina
ABSTRACT- The role of predator diversity in regulating community structure and ecosystem processes is not well understood. We manipulated predator identity and diversity to test for direct and indirect effects on herbivores and plant community diversity and biomass accumulation. In mesocosms, we assembled food webs using organisms of a benthic marine habitat in North Carolina. We found that predator species have unique effects on community structure, and the strength and nature of a trophic cascade can change with predator diversity. When omnivores were included in the diverse predator assemblages, increasing predator diversity decreased plant biomass. Omnivorous fish directly altered plant composition by preferentially feeding on different algae than specialist, macroinvertebrate herbivores. Preliminary results indicate that when diverse predator mixtures do not include omnivores, predator diversity strengthens the trophic cascade and results in high plant biomass and altered plant composition. Thus, the direction and mechanism of predator diversity effects may depend on whether the predator assemblage includes omnivores. In addition, predators had indirect effects on plant community composition through species-specific prey preference. In natural systems, over-harvesting and habitat loss have reduced predator diversity in a wide variety of ecosystems. Cascading effects of this decline in diversity at top trophic levels can lead to dramatic changes in plant community structure.
Key words: diversity, ecosystem functioning, trophic cascade, predator