Cascading effects of predator richness

www.frontiersinecology.org W know that predators play a vital role in maintaining the structure and stability of communities and that their removal can have a variety of cascading, indirect effects (Terborgh et al. 2001; Duffy 2003; Figure 1). But how important is predator richness? Are the numbers of predator genotypes, species, and functional groups ecologically important properties of predator assemblages? Ecologists have recently begun to address this question by exploring the many potential links between predator richness and the structure and dynamics of lower trophic levels. The initial phases of research on the effects of biodiversity on ecosystem functioning (BEF) focused almost exclusively on single trophic level systems comprised primarily of terrestrial plants. While these studies formalized and explored the idea that biodiversity can regulate key properties of communities and ecosystems, there is a growing belief that the failure to incorporate consumers into BEF research has led to overly simplistic conclusions (Paine 2002). Ecologists have therefore begun to explore the effects of changing biological richness at higher trophic levels, and BEF research is rapidly expanding into a more realistic, multi-trophic context (Duffy et al. 2007). Here, we review the emerging field of predator biodiversity research, as well as the underlying mechanisms through which predator richness can affect lower trophic levels and ecosystem properties. We then consider how to apply lessons learned from theoretical and experimental predator richness studies to habitat and ecosystem conservation and management.