Functional Ecology 2009, 23, 4–16 doi: 10.1111/j.1365-2435.2008.01522.x © 2009 The Authors. Journal compilation © 2009 British Ecological Society Blackwell Publishing Ltd NUTRITIONAL ECOLOGY Nutrition, ecology and nutritional ecology: toward an integrated framework David Raubenheimer 1 *, Steven J. Simpson 2 and David Mayntz 3,4 1 Institute of Natural Resources and New Zealand Institute for Advanced Study, Massey University, Albany, New Zealand; 2 School of Biological Sciences, University of Sydney, Sydney, Australia; 3 Department of Ecology and Genetics, University of Aarhus, Aarhus, Denmark; and 4 Department of Zoology, University of Oxford, Oxford, UK Summary 1. The science of nutritional ecology spans a wide range of fields, including ecology, nutrition, behaviour, morphology, physiology, life history and evolutionary biology. But does nutritional ecology have a unique theoretical framework and research program and thus qualify as a field of research in its own right? 2. We suggest that the distinctive feature of nutritional ecology is its integrative nature, and that the field would benefit from more attention to formalizing a theoretical and quantitative framework for developing this. 3. Such a framework, we propose, should satisfy three minimal requirements: it should be nutritionally explicit, organismally explicit, and ecologically explicit. 4. We evaluate against these criteria four existing frameworks (Optimal Foraging Theory, Classical Insect Nutritional Ecology, the Geometric Framework for nutrition, and Ecological Stoichiometry), and conclude that each needs development with respect to at least one criterion. 5. We end with an initial attempt at assessing the expansion of our own contribution, the Geometric Framework, to better satisfy the criterion of ecological explicitness. Key-words: nutritional models, nutritional ecology, optimal foraging theory, ecological stoichiometry, geometric framework Introduction The range of studies that go by the label ‘nutritional ecology’ encompasses an impressive diversity of taxa, methods, concepts, interests and goals, spanning, inter alia, behaviour, morphology, developmental biology, physiology, life history, ecology and evolution, with emphasis both on function and on mechanism. Such cross-disciplinary breadth pro- vides broad conceptual and methodological foundations, and imbues the discipline with wide-ranging relevance. But it also presents challenges. Foremost among these is that to progress beyond the status of label and qualify as a field of research in its own right (Shettleworth 2000), nutritional ecology needs an identity more distinct than a diffuse con- fluence of methods and interests united within the general areas of nutrition and ecology. What would be the cornerstone of that identity? In our judgement, the single most distinctive characteristic of nutritional ecology is its propensity to probe the gaps between disparate fields, yielding integrative insights that would otherwise not be obtained. The hiatus that is most closely associated with the subject is that between field ecology (e.g. resource quality and distribution) and animal phenotypes (e.g. foraging behaviour, functional morphology, digestive physiology). Progress in bridging this gap has, however, been piecemeal and incomplete, as is evidenced by growing concern in the literature for greater integration between the study of phenotypes and ecology (e.g. Jones & Lawton 1995; Fryxell & Lundberg 1997; Olff et al. 1999; McGill et al. 2006; Schmitz 2008). We believe that nutritional ecology would be better equipped for achieving this integration if more attention was paid to developing frameworks that system- atically define the panoply of salient components in organism– environment interactions and explicitly model their inte- gration. In other words, frameworks are needed that provide a scaffold for melding nutrition and ecology into an integrated nutritional ecology. The primary aim of this article is to state what we consider to be the necessary basic properties of such a scheme, and evaluate in relation to these some frameworks that are currently in use: Optimal Foraging Theory, Classical Insect Nutritional Ecology, the Geometric Framework for nutrition, *Corresponding author: E-mail: d.raubenheimer@massey.ac.nz