Measuring the occurrence and strength of intraguild predation in modern food webs

Pahl, K. Blue; Yurkowski, David J.; Lees, Kirsty J.; Hussey, Nigel E.

doi:10.1016/j.fooweb.2020.e00165

Cited by 9 publications

(17 citation statements)

References 172 publications

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“…We found evidence that these two disruptive interactions might reinforce one another, as detection of thrips DNA in predators was reduced both in the presence of abundant arthropod prey and with increasing abundance of predators perhaps drawn to those prey. This reinforces the complexity of feedbacks that might be seen in open field situations, where prey and predator abundance interact with one another in complex ways (Paul et al, 2020). Molecular gut content analysis, despite its limitations, may be a particularly powerful tool to detect these relationships against the high background arthropod diversity typical of real agricultural fields.…”

Section: Discussionmentioning

confidence: 62%

“…Another complexity when considering generalist predators as biocontrol agents, is that they often feed on one another in addition to pests (Rosenheim, 1998;Paul et al, 2020). Intraguild predation is most disruptive when a predator both infrequently feeds on the pest and heavily attacks the pest's key natural enemy (Finke and Denno, 2004;Ives et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

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Alternative Prey and Predator Interference Mediate Thrips Consumption by Generalists

et al. 2022

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Generalist predators’ complex feeding relationships make it difficult to predict their contribution to pest suppression. Alternative prey can either distract predators from attacking pests, weakening biocontrol, or provide food that support larger predator communities to enhance it. Similarly, predator species might both feed upon and complement one another by occupying different niches. Here, we use molecular gut-content analysis to examine predation of western flower thrips (Frankliniella occidentalis) by two generalist predatory bugs, Geocoris sp. and Nabis sp. We collected predators from conventional and organic potato fields that differed in arthropod abundance and composition, so that we could draw correlations between abundance and biodiversity of predators and prey, and thrips predation. We found that alternative prey influenced the probability of detecting Geocoris predation of thrips through a complex interaction. In conventionally-managed potato fields, thrips DNA was more likely to be detected in Geocoris as total abundance of all arthropods in the community increased. But the opposite pattern was found in organic fields, where the probability of detecting thrips predation by Geocoris decreased with increasing total arthropod abundance. Perhaps, increasing abundance (from a relatively low baseline) of alternative prey triggered greater foraging activity in conventional fields, but drew attacks away from thrips in organic fields where prey were consistently relatively bountiful. The probability of detecting Geocoris predation of thrips generally increased with increasing thrips density, but this correlation was steeper in organic than conventional fields. For both Geocoris and Nabis, greater Nabis abundance correlated with reduced probability of detecting thrips DNA; for Nabis this was the only important variable. Nabis is a common intraguild predator of the smaller Geocoris, and is highly cannibalistic, suggesting that predator-predator interference increased with more Nabis present. Complex patterns of thrips predation seemed to result from a dynamic interaction with alternative prey abundance, alongside consistently negative interactions among predators. This provides further evidence that alternative prey and predator interference must be studied in concert to accurately predict the contributions of generalists to biocontrol.

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Section: Discussionmentioning

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Alternative Prey and Predator Interference Mediate Thrips Consumption by Generalists

et al. 2022

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“…A better quantitative understanding of IGP can provide critical insights into the complex predator-predator-prey trophic interactions and could help predict the community structure and stability (Arim and Marquet 2004;Nakazawa and Yamamura 2006;Pahl et al 2020).…”

Section: Resultsmentioning

confidence: 99%

An Experimental Framework for Determining the Degree of Intraguild Predation in a Three-Species Omnivorous Food Web in the Field

Hsu

2022

Preprint

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Intraguild predation (IGP) is common in natural and human-managed systems and plays a critical role in food web dynamics. Previous studies have documented the occurrence of IGP across a wide range of predator taxa, yet there is still a lack of quantitative understanding regarding the degree/intensity of IGP in these systems. Here, I propose an experimental framework combining controlled feeding trials and stable isotope analysis to determine the degree of IGP in a three-species omnivorous food web (shared prey + mesopredator + top predator) in the field. The degree of IGP is defined herein as the proportion (in number) of mesopredator consumed in the total diet (shared prey + mesopredator) of top predator. The feeding trials are used to construct a standard curve for the degree of IGP in the focal system, to which the stable isotope signatures of field samples are compared to estimate the degree of IGP in the field. The proposed framework leverages the strengths of different experimental approaches to studying trophic interactions, providing a useful tool for quantifying IGP in a more accurate (controlled feeding trials and standard IGP curve) and realistic (stable isotope analysis of field samples) fashion. If proven successful, the current framework can be extended to food webs involving more complex interactions (e.g., cannibalism and multiple shared prey) and further complemented with other approaches (e.g., molecular gut content analysis) to capture a more complete picture of IGP dynamics in the field.

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“…When pests are not the preferred prey, generalists might focus their attacks on more appealing options and abandon any contribution to biological control 5–8 . Most troubling, perhaps, is that generalist predators often feed on other natural enemies 9–11 . In extreme cases, for example when an aggressive intraguild predator feeds heavily on a key specialist natural enemy, generalists can allow herbivores to escape top‐down control 12–14 .…”

Section: Introductionmentioning

confidence: 99%

Alternative prey mediate intraguild predation in the open field

Snyder

Smith

Chapman

et al. 2022

Pest Management Science

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BACKGROUND: Generalist predators that kill and eat other natural enemies can weaken biological control. However, pest suppression can be disrupted even if actual intraguild predation is infrequent, if predators reduce their foraging to lower their risk of being killed. In turn, predator-predator interference might be frequent when few other prey are available, but less common when herbivorous and detritus-feeding prey are plentiful. We used molecular gut-content analysis to track consumption of the predatory bug Geocoris sp. by the larger intraguild predator Nabis sp., in organic and conventional potato (Solanum tuberosum) fields.RESULTS: We found that higher densities of both aphids and thrips, two common herbivores, correlated with higher probability of detecting intraguild predation. Perhaps, Nabis foraging for these herbivores also encountered and ate more Geocoris. Surprisingly, likelihood of intraguild predation was not strongly linked to densities of either Nabis or Geocoris, or farming system, suggesting a greater importance for prey than predator community structure. Intriguingly, we found evidence that Geocoris fed more often on the detritus-feeding fly Scaptomyza pallida with increasing predator evenness. This would be consistent with Geocoris shifting to greater foraging on the ground, where S. pallida would be relatively abundant, in the face of greater risk of intraguild predation. CONCLUSION: Overall, our findings suggest that while herbivorous prey may heighten intraguild predation of Geocoris in the foliage, detritivores might support a shift to safer foraging on the ground. This provides further evidence that prey abundance and diversity can act to either heighten or relax predator-predator interference, depending on prey species identity and predator behavior.

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Measuring the occurrence and strength of intraguild predation in modern food webs

Cited by 9 publications

References 172 publications

Alternative Prey and Predator Interference Mediate Thrips Consumption by Generalists

Alternative Prey and Predator Interference Mediate Thrips Consumption by Generalists

An Experimental Framework for Determining the Degree of Intraguild Predation in a Three-Species Omnivorous Food Web in the Field

Alternative prey mediate intraguild predation in the open field

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