Grégory will be mainly involved in the task 2,2 from WP2: "Effects of biodiversity and biodiversity management on pest control processes".
The intensity of pest control relies to a great extent on the community structure in which pests and their natural enemies are embedded. The structure of the community of plants affects other communities, with direct bottom-up effects (quantity and quality of primary resources supporting food webs) and with indirect effects especially through the modification of habitats. Disentangling how plant diversity alters the functioning of communities and pest control is not easy task due to the difficulty involved in measuring real interactions in natura. We will use DNA metabarcoding to identify trophic link occurring between consumers and resources (including pests) within the complex network of the agroecosystem. This method leads to a full reconstruction of the food web structure and enables a comprehensive analysis of the pest regulation processes (Mollot et al. 2014). The use of the method in a set of contrasted situations is one of the most ambitious initiatives in community ecology applied to agroecosystems. Since the method will be applied strictly using exactly the same protocols across sites, our dataset will provide a generic understanding of the relationship between plant diversity, the structure of food webs and pest control. We will focus on the most important pests in each type of agroecosystem: white grubs in rice, banana weevil and root-feeding nematodes, aphids in fruit orchards, and the coffee borer. In parallel, in each situation investigated, pest abundance will be measured to quantify the control provided by the community. DNA will be extracted from dietary samples, followed by cloning, sequencing, and finally taxonomic assignment of sequences, which will make it possible to establish binary matrices of resource-consumer events. From a practical point of view, DNA metabarcoding will help identify species directly involved in pest control along with other species that may interfere with them (for instance through intra-guild predation), thus feeding the model created in WP3.
Finally, the structure of food webs and the pest regulation potential will be analyzed as a function of PFD and management options.