Frederico Mestre, Dominique Gravel, David García-Callejas, Carla Pinto-Cruz, Miguel G. Matias, Miguel B. Araújo

Food webs represent energy fluxes and nutrient cycling between interacting species, underpinning ecosystem functioning. Whether and how interactions vary over environmental gradients is still largely unknown. We reviewed the literature searching for systematic relationships between structural food-web properties and environmental gradients. Temperature and biotic factors are amongst the most addressed drivers in determining structural food web properties. Most studies are local, replication is often lacking, and regional generalities are difficult to derive. The lack of a consistent theory predicting how food webs change across environmental gradients, the diversity of objectives in food-web studies, and the absence of a standardized methodology for studying them severely limit progress in the field. Moving forward requires the establishment of a core set of testable predictions, agreed standards for data collection and analysis, and the development of geographically distributed experimental studies of food-webs dynamics.