The Influence of Intraguild Predation on Prey Suppression and Prey Release: A Meta-Analysis

Abstract

Intraguild predation (IGP) occurs when one predator species consumes another predator species with whom it also competes for shared prey. One question of interest to ecologists is whether multiple predator species suppress prey populations more than a single predator species, and whether this result varies with the presence of IGP. We conducted a meta-analysis to examine this question, and others, regarding the effects of IGP on prey suppression. When predators can potentially consume one another (mutual IGP), prey suppression is greater in the presence of one predator species than in the presence of multiple predator species; however, this result was not found for assemblages with unidirectional or no IGP. With unidirectional IGP, intermediate predators were generally more effective than the top predator at suppressing the shared prey, in agreement with IGP theory. Adding a top predator to an assemblage generally caused prey to be released from predation, while adding an intermediate predator caused prey populations to be suppressed. However, the effects of adding a top or intermediate predator depended on the effectiveness of these predators when they were alone. Effects of IGP varied across different ecosystems (e.g., lentic, lotic, marine, terrestrial invertebrate, and terrestrial vertebrate), with the strongest patterns being driven by terrestrial invertebrates. Finally, although IGP theory is based on equilibrium conditions, data from short-term experiments can inform us about systems that are dominated by transient dynamics. Moreover, short-term experiments may be connected in some way to equilibrium models if the predator and prey densities used in experiments approximate the equilibrium densities in nature.

Interactions among predators and the cascading effects of vertebrate insectivores on arthropod communities and plants

“…Current theory successfully emulates the trophic dynamics operating within arthropod communities (15), but our findings show they are not extensible to predict effects of vertebrate insectivores in these terrestrial systems. Vertebrate insectivores such as birds, bats, and lizards reduce the densities of both predaceous and herbivorous arthropods according to their proportional representation in the arthropod community.…”

“…This result is especially noteworthy given the overwhelming evidence that arthropod predators and parasitoids themselves are capable of suppressing herbivore populations (2,3,26). Theory on intraguild predation predicts that intermediate predators should buffer and weaken the net effects of top predators upon herbivores (21), and empirical evidence from arthropod food webs supports this prediction (15). Our contrary findings thus suggest that current models of trophic interactions do not adequately describe dynamics involving vertebrate insectivores.…”

“…To the extent that these meta-analyses included vertebrate insectivores, they emphasized effects on herbivores, and the role of predatory arthropods as mediators of trophic cascade strength has not been studied. Vance-Chalcraft et al (15) investigated the consequences of intraguild predation for herbivore suppression, but their review included few studies on vertebrate insectivores and did not address the indirect effects of such dynamics for plants. Consequently, fundamental aspects of how vertebrate insectivores affect arthropods and plants remain unclear, despite extensive evidence for the importance of vertebrate insectivores (10,16,17).…”

How functional response and productivity modulate intraguild predation

“…IGP is a widespread interaction in natural and managed ecosystems (Arim and Marquet 2004) that may influence the structure and dynamics of communities (Holt and Polis 1997, Morin 1999, Mylius et al 2001, Vance-Chalcraft et al 2007 and, from an applied perspective, the outcome of biological control and the management of endangered or exotic invasive species (Rosenheim et al 1995, Rosenheim 1998, Mü ller and Brodeur 2002, Vance-Chalcraft et al 2007, Straub et al 2008. Following the publication of a general theory of IGP by Holt and Polis (1997), several models and empirical studies have investigated the nature and prevalence of IGP in diverse terrestrial and aquatic communities.…”

Human-Altered Mesoherbivore Densities and Cascading Effects on Plant and Animal Communities in Fragmented Tropical Forests

“…Trophic cascades, wherein perturbations of apex predator populations cascade down to affect lower consumer (e.g., herbivore) and producer (i.e., plant) levels (Paine, 1980), were once thought not to occur in tropical forests as a result of their high species diversity and high intraguild predation, leading to functional redundancy and weak links between individual predator and prey species (Polis & Holt, 1992;Polis & Strong, 1996;Shurin et al, 2002;Strong, 1992;Van Bael et al, 2003;Vance-Chalcraft et al, 2007). Terborgh (1992) first presented evidence suggesting a carnivore (jaguar, Panthera onca; puma, Puma concolor) -large seed predator (peccary, Pecari spp.…”