Experimental Approaches to Understanding the Relationship Between Predator Biodiversity and Biological Control

Abstract

Conservation biological control (CBC) involves the manipulation of the environment to favour the natural enemies of pests. Alternative agricultural practices, such as organic farming, are more biodiversity-friendly than conventional agricultural practices and generally lead to greater predator species richness and abundance. This is desirable from a conservation perspective, but it is unclear how greater predator diversity affects biological control. Unfortunately, the predator ecology literature provides little guidance: increasing the number of predator species has been shown to enhance, diminish, and not affect prey suppression. In this chapter we explore how the experimental approach used in biodiversity and ecosystem functioning (BEF) studies, which focus on the ecological consequences of species loss, may be used to study how increasing predator diversity affects biological control. The notable features of this approach are: 1) realistic levels of species richness (i.e., < 2 predator species), 2) the use of substitutive, rather than additive, experimental designs, and 3) experimentally distinguishing the effect of species richness from the effects of species abundance, composition, and identity. This experimental approach can be used to identify which components of predator biodiversity—species richness, abundance, composition, and identity—should be targeted by CBC practitioners to maximize pest suppression. Further, it can be used to assess whether predator biodiversity conservation and biological control are truly compatible goals. Ultimately, we hope that this chapter will serve to motivate future research into this important problem.