Addition of a new resource in agroecosystems: Do cover crops alter the trophic positions of generalist predators?
Duyck, Pierre-François | Lavigne, Anaïs | Vinatier, Fabrice | Achard, Raphaël | Okolle, Justin N. | Tixier, Philippe
Generalist predators can play an important role in agroecosystems by controlling herbivores via top-down effects. As cover crops are increasingly used in agroecosystems, the effects of this resource on generalist predator diet need to be evaluated. We studied the effect of adding a cover crop, Brachiaria decumbens, on trophic niches of generalist predators in a banana agroecosystem by analysing stable isotope variation in C and N for Cosmopolites sordidus, a major banana pest, and its potential predators (spiders, ants, centipedes, and earwigs). While addition of the new resource did not change the trophic niche of the banana pest C. sordidus, the trophic position of the generalist predators was changed as indicated by δ¹³C signature. Cover crop provided resources that are likely to support a community of insect herbivores, which are alternative preys for generalist predators. The failure of the cover crop to increase δ¹⁵N signature is inconsistent with the hypothesis that the cover crop would increase intraguild predation. By providing alternative preys, the addition of a new resource in agroecosystems has the potential to increase populations of generalist predators and therefore pest control.
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