Austral Ecology (2019) 44, 1065-1075

Dalila Rendon, Phillip W. Taylor and Mary E.A. Whitehouse (2019)
Multiple intraguild predators reduce mortality risk of a mutual agricultural pest prey in simple, but not in complex, experimental settings
Austral Ecology 44 (6), 1065-1075
Abstract: Multiple predator species that coexist with each other and their mutual prey can have combined effects on prey mortality that are similar to the sum of each predator's individual impact (linear effects), greater than the sum of each predator's individual impact (risk enhancement), or less than the sum of each predator's individual impact (risk reduction). Understanding multiple predator effects is important to determine the impact of predators on pest prey in agroecosystems. If two predators share the same broad spatial domain and hunting mode and engage in intraguild predation, then their combination is expected to result in risk reduction for a mutual prey. We tested this hypothesis using both additive and replacement experimental designs on two species of generalist wolf spider predators (Tasmanicosa leuckartii and Hogna crispipes) that hunt in the same domain, and a mutual insect prey (cotton bollworm Helicoverpa armigera). We used two types of enclosures: a small simple laboratory enclosure, and a larger more complex cotton plant enclosure. We found that in the small simple laboratory enclosures, the presence of two spiders led to risk reduction of Helicoverpa larva mortality as expected, but in larger more complex cotton plant enclosures the presence of both species resulted in linear effects rather than risk reduction on Helicoverpa mortality. Furthermore, intraguild predation did not change multiple predator effects in laboratory or plant enclosures. This study has implications for managing arthropod predators in agroecosystems; contrary to predictions of ecological frameworks, coexistence of predators that share the same hunting mode and hunting domain may not lead to risk reduction on a mutual prey in more complex environments, where encounters among predators can be lower. Conservation of multiple predators of a single guild can play an essential role on biological control of insect pests.
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Link to article at publishers website
Database assignments for author(s): Phillip W. Taylor, Mary E.A. Whitehouse

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
environment/habitat manipulation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Helicoverpa armigera
Hogna crispipes (predator)	Helicoverpa armigera
Tasmanicosa leuckartii (predator)	Helicoverpa armigera