The importance of intraguild predation in predicting emergent multiple predator effects

Abstract

Prey typically coexist with multiple predator species, each of which presents a predation risk related to its habitat domain and foraging mode. These predator characteristics can be used to predict how the risk from multiple predators will combine to create emergent multiple predator effects for shared prey. Interactions between predators, particularly intraguild predation, can strongly alter prey suppression, though the importance of intraguild predation in multiple predator effects has not been explicitly explored. Furthermore, the vast majority of studies on multiple predator effects has focused on shared prey that are herbivorous, thus experiments focused on mesopredators are needed to evaluate the generality of conclusions made about multiple predator effects. We used a suite of carnivorous arthropods to test a predictive framework of multiple predator effects and to evaluate the role of intraguild predation in shaping these effects. We allowed the wolf spiders Pardosa milvina, Tigrosa helluo, and Rabidosa rabida and the ground beetle Scarites quadriceps to interact and recorded the outcome of all predatory events. We used two tests of multiple predator effects to determine whether predators created risk enhancement, risk reduction, or were substitutable. We found that the occurrence of intraguild predation decreased the overall risk to prey, causing observed multiple predator effects to deviate from predictions. Additionally, we highlight the importance of considering predator identity, as predators were capable of increasing, decreasing, or not altering the success of their competitors. Our study demonstrates that intraguild predation is a critical factor in determining how the risk from multiple predators will combine to affect their prey.

Warming reverses top-down effects of predators on belowground ecosystem function in Arctic tundra

“…Alternatively, under elevated wolf spider densities, warming-associated increases in spider activity could result in more frequent antagonistic interactions with other predators (66). Strong predator-predator interactions or even intraguild predation, which is fairly common in this system (22), can relax the collective effect of predator communities, resulting in increased prey populations and weaker trophic cascades (67,68). Under warming, we observed that numbers of intermediate predators declined as wolf spider densities increased (Fig.…”

Predator cues have contrasting effects on lifespan ofPardosa milvina(Araneae: Lycosidae)

“…Increased longevity in response to predator cues has not previously been documented, but may be related to interactions between Tigrosa and Scarites. Tigrosa is the more dangerous predator for Pardosa (Sitvarin, unpublished data), though Scarites is capable of interfering with and consuming Tigrosa (Sitvarin & Rypstra 2014). Therefore, Pardosa may interpret Scarites cues as a forthcoming reduction in predation risk, leading to decreased levels of stress hormones or elevated levels of hormones that counter the effects of stress hormones.…”

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“…The main orders constituting Lycosid diets in our study were Diptera, Hemiptera, Hymenoptera and Lepidoptera. Interestingly, spiders, harvestmen and carabid beetles were also found in spider gut contents which confirms the potential of NoSpi2 for the investigation of intraguild predation, which has often been documented among spiders and for carabid beetles feeding on spiders (Lang, 2003;Davey et al, 2012;Sitvarin & Rypstra, 2014). Although coleopterans have been reported as spider prey (Hambäck et al, 2016), predation of carabid beetles by spiders has not been observed so far.…”