Our understanding of ecosystem functioning is strongly linked to the study of predator-prey relationships and food web structures. However, trophic ecology has often focused on identifying taxonomic relationships and quantifying the biomass or energy ingested by consumers, but has often failed to integrate the importance of the nutritional quality of resources in ecological dynamics. Underlying this gap is the multi-dimensional nature of resource quality which has hampered any consensus on the definition of resource nutritional quality. In this special issue, we aimed at gathering a subset of articles exemplifying the diversity of variables by which resources quality is quantified, the diversity of research topics that can be tackled in ecology - from physiological or evolutionary aspects to ecosystem processes - and propose some perspectives on the integration of nutritional quality within broader ecological concepts. Using a semi-automated literature analysis, we map the current landscape of the “resources nutritional quality” research of the last 30 years. We depict how it has been quantified through physical, biological or chemical indicators, the use of these parameters being largely dependent on the type of ecosystem studied and on the investigated ecological process. We then position the articles published in this special issue of Oikos within this landscape, showing they cover a small but relatively well representative subset of the domains of resources quality-related issues. Articles in this special issue browse a range of individual and population-level approaches (embracing evolutionary questions) to community related questions, include methodological issues and ecosystem-wide approaches using trophic quality indicators as tracers of resources origin. Based on these studies and on the literature review, we identify a non-exhaustive list of challenges and perspectives of research that we consider of highest priority in the large topic of trophic ecology.

Web of Science search (1991-2020) using the terms ("nutrition* quality" OR "quality prey" OR "quality food" OR "quality resource*" OR "diet quality"  OR "resource* quality"  OR "food quality"  OR "prey* quality") and restricting Web of Science categories to fields related to environmental sciences and Ecology. This research, was conducted on 20 November 2020.

N/A correspond to missing data