Combining stable isotopes analyses with next generation sequencing to disentangle trophic links in banana agroecosystem

Bottom-up and top-down effects are recognized to be important mechanisms structuring food-web in ecosystems. A new resource added to an agroecosystem, as a cover crop, may support alternative preys which affect feeding behavior of generalist predators and natural regulation of pests. We studied the effect of adding a cover crop, Brachiaria decumbens, on the diet of herbivores and predators in a banana agroecosystem in order to emphasize interactions of a major pest, Cosmopolites sordidus, with other species of the system. We used stable isotopes analysis (C and N) to determine trophic levels and origin of carbon consumed, and molecular markers (shortened region of trnL chloroplastic marker for plants, and CO1 mitochondrial gene for arthropods) to decipher qualitative composition of gut contents of each species. We showed that diet of herbivores and predators are modified by the addition of the new basal resource. This has consequences for the predation of the pest. This dual approach allowed us to build an almost complete food-web of banana agroecosystem that is a starting point to model these interactions and design cropping system maintaining low occurrence of pests.