Biodiversity and Conservation 13: 1791–1793, 2004. # 2004 Kluwer Academic Publishers. Printed in the Netherlands.

Book Review Ecological Niches: Linking Classical and Contemporary Approaches Jonathan M. Chase and Mathew A. Leibold, University of Chicago Press, Chicago, IL, 2003, 212 pp., ISBN 0-226-10180-0, US$20.00. The idea that the outcomes of species interactions are predictable and have mechanistic underpinnings is highly attractive. A framework for such predictions would surely empower community ecology as a predictive science and would facilitate our understanding of diversity patterns. This would also bring to conservation biologists the ability to reach precise conclusions and make suitably informed decisions. Thus even before I opened this book, I was caught by the blurb on the back cover: high praise from Robert Holt, with a particularly interesting final sentence: ‘This book provides one avenue, paving the way towards a revitalization of community ecology’. If community ecology is, in fact, in the doldrums, then how might this book help? And does this book mark the beginning of the new science of community ecology? Holt’s quote, I think, reflects the perception that community ecology needs something. The field has recently gone through critical introspection concerning its ability to understand community-level patterns (e.g., Lawton 1999). At the same time, some community ecologists may be reacting to the perceived powerful role for Hubbell’s (2001) neutral theory. Chase and Leibold do indeed inform the reader that their book is, in part, a response to Hubbell’s theory (that communities are governed according to ‘neutral’ rules), but their book is interesting for other reasons, too. The central concept of the book builds on previous work by Tilman (1982) and Leibold (e.g., 1995, 1996), which the authors seem to have elevated to paradigm status in ecology. They succinctly review the history of the niche in community ecology. Their thesis is simple: that the two traditions that have defined the niche (i.e., Hutchinsonian, a species’ environmental needs; and Eltonian, a species’ impacts on the environment) are antithetical, and that a dialectic, or synthetic approach, is a better way to understand the notion of the niche. ‘Better’ implies that by incorporating both needs and impacts, we can develop a deeper, more mechanistic understanding of patterns of species’ coexistence. The measure of the dialectical niche provided by Chase and Leibold is essentially the Zero Net Growth Isocline (ZNGI) and its impact vector, inferred from a graph with two axes – representing any factors essential to the population dynamics of a species. This may be, for example, two orthogonal resources, or a single limiting resource and predation pressure, or perhaps a resource with a stress, or disturbance level. They state: ‘The niche is described by the ZNGI of an organism along with its impact vectors in the multivariate space defined by the set of environmental factors that are present’ (p. 31). From this framework they seek to predict the outcome of species competition for

1792 shared resources, based on Tilman’s (1982) R* principle, which holds that a species that can reach an equilibrium at the lowest resource level will competitively exclude other species competing for that resource. Chase and Leibold extend this concept in interesting ways to explain an assortment of important ecological phenomena, such as species sorting, succession, and the ‘intermediate disturbance hypothesis’. This book is concise, and could have benefitted from a more thorough treatment of its topics. Chapters 1–4 do a great job of introducing the major themes and concepts, and orienting the ideas toward the ZNGI approach. I think their review of the niche concept (Chapter 1) is excellent. However, Chapters 5–9 (the application of the ZNGI approach to various ecological phenomena) seem to me to cover too many phenomena with too little analysis. These chapters do not examine the breadth of ideas, or the published literature enough to give the reader a sense of confidence in the explanations provided. That said, these chapters do cover some of the most important phenomena in ecology, which any synthetic theory would need to embrace. Chapter 10 examines the evolutionary realm of the ZNGI-based niche, and, while very interesting, might have been developed further, since any strong ecological programme must include evolutionary implications and underpinnings, in order to unify patterns in nature. The fundamental value of their paradigm may concern some readers. Not to say that they are necessarily wrong, but rather that their application of the ZNGI approach at times seems to lack rigor, and appears overly sweeping. While showing how the ZNGI approach may explain ecological phenomena, they present very little data and virtually no empirical tests of the ZNGI approach. It reads a bit like the proverbial ‘just so’ stories. Some of the extensions of the ZNGI approach are almost untestable, especially once the various vagaries of environmental variability, and stochastic processes are incorporated. The authors recognize this: ‘The utility of our models lies not with the direct testability or validity of all of their assumptions and predictions, but with their ability to serve as a springboard for a variety of important insights and syntheses’ (p. 61). I believe that any advance in niche ‘theory’ will need to take the form of a scientific theory. This entails the usual rigorous consequences – novel predictions, scope, precision and accuracy, as well as testability (Brown 2001). I’m afraid that without a core of testability, proponents of the ZNGI approach may be forced to construct an array of ad hoc hypotheses (sensu Lakatos 1970), which may not be constructive for the founding of an important research programme. (This may in part be why community ecology is already in so inchoate a condition as it is!) If (by authors’ own admission) the content of this book does not represent a rigorous scientific theory, what about the goal of creating a springboard for community ecology? Tilman’s (1982) book was also concerned with species competition and community structure and also used the ZNGI premise to probe it. Chase and Leibold do develop further these ideas. The ideas presented in Tilman’s book were the impetus for much useful investigation of competition, over the past twenty years (e.g., Fox 2002). Now, whether due to conceptual issues or practical difficulties with testing ZNGI predictions, the ideas have not reached ‘paradigm status’ in ecology. We shall need to wait and see whether the Chase–Leibold repackaging has better success.

1793 Does this book ‘pave the way toward a revitalization. . .’? I think that only future hindsight will answer this question. However, where this book should succeed is in fostering certain hypotheses and stimulating new questions. Graduate students and working ecologists will benefit from reading this book (as they would from reading its targeted volume – Hubbell 2001).

References Brown J.R. 2001. Who Rules in Science? An Opinionated Guide to the Wars. Harvard University Press, Cambridge, Massachusetts. Fox J.W. 2002. Testing a simple rule for dominance in resource competition. American Naturalist 159: 305–319. Hubbell S.P. 2001. The Unified Neutral Theory of Species Abundance and Diversity. Princeton University Press, Princeton, New Jersey. Lakatos I. 1970. Falsification and the methodology of scientific research programmes. In: Lakatos I. and Musgrave A. (eds) Criticism and the Growth of Knowledge. Cambridge University Press, Cambridge, UK, pp. 91–196. Lawton J.H. 1999. Are there general laws in ecology? Oikos 84: 177–192. Leibold M.A. 1995. The niche concept revisited: mechanistic models and community context. Ecology 76: 1371–1382. Leibold M.A. 1996. A graphical model of keystone predators in food webs: trophic regulation of abundance, incidence, and diversity patterns in communities. American Naturalist 147: 784–812. Tilman D. 1982. Resource Competition and Community Structure. Princeton University Press, Princeton, New Jersey.

Marc W. Cadotte Complex Systems Group Ecology and Evolutionary Biology University of Tennessee Knoxville, TN 37996, USA