Measuring the occurrence and strength of intraguild predation in modern food webs
Abstract
Intraguild predation (IGP) is a complex, multi-species interaction that simultaneously combines predation and competition among a minimum of three individuals - a predator (IGpredator) that kills and consumes prey (IGprey) with which it competes for a common resource, resulting in a ‘trophic loop’. Although ubiquitous, IGP occurrence and strength vary across functional groups, trophic levels and ecosystems. A form of omnivory, changes to IGP trophic loops can have non-linear consequences that shape individual-, population- and community-level processes. This review i) synthesizes current knowledge on the methods available to measure the occurrence and strength of IGP in food webs from qualitative observation to complex quantitative models and ii) uses a two-tier approach to quantify research effort since the seminal work of Polis et al. (1989), and highlights important areas for future IGP research. Modern technological advancements, including diverse chemical tracers, telemetry with integrated sensors, and simulation modelling provide novel methods to address IGP knowledge gaps and improve understanding of how food webs will respond to perturbations. At the individual level, chemical and morphological changes in response to IGP require further study, while population- and community-level analyses require a focus on the resilience of common resources and changes in guild structure, respectively. The application of novel methods to investigate IGP will result in an improved understanding of the underlying mechanisms responsible for ecosystem function.