Old wine in a new bottle:The Struggle for Existence by G.F. Gause. Reprinted by Dover Publications, 2003. US$35.00, hbk (164 pages) ISBN 0 486 49520 5

This classic book is now back in print in a new hardcover edition, which should enable current graduate students and researchers to acquaint themselves with this beautiful piece of work. Reviewing it is a pleasure, as many of the insights are so timely that parts of the book read as though it could have been just written. It is also illuminating to consider what parts are out of date, or more precisely what would be added to the volume if it were written today. At least two recent volumes ([1] and especially [2]) take a similar approach to population biology, with a focus on both laboratory experiments and integration with mathematical models. Yet, I would argue that most students of population ecology would profit by carefully reading Gause’s volume in spite of its age. I have had occasion over many years to go back to The Struggle for Existence, but have typically focused on the more detailed experimental descriptions, so my rereading of Gause’s statement of ‘the problem’ was particularly enjoyable. The overall approach he advocates, of explaining the existence of species in terms of elementary processes, is probably not appreciated enough by modern practitioners. His understanding of the difference between experiments with a closed system, versus those where energy in some form is continually added, is also important. An issue that he raises, of the need to close the gap between biologists and mathematicians, is one that has yet to be solved [3]. Yet, Gause recognized that progress depended on both approaches working together. A careful read through the whole volume reveals just how many fundamental ecological principles and idea, many of which were ‘discovered’ much later, are in fact covered in the pages of this slim volume. For example, the ideas that later become known as the difference between ‘r’ selection and ‘K’ selection are covered in the summary on page 113. As Gause phrases it, in the first period of competition, species compete for unutilized resources, namely r selected competition. In the second period, completely utilized energy is redistributed among species, which is the K selected period. Of course, the full treatment of competition is also of great interest. The consideration of the outcome of the interaction between predator and prey populations, and the questions raised by the laboratory experiments, are, of course, one of the most important (and well known) parts of the volume. Gause emphasizes the importance of immigration (and presumably emigration) for the persistence of predator and prey, as would later investigators, following the lead of Huffaker. The emphasis on underlying environmental heterogeneity is important, and a perhaps still neglected issue for theoretical ecologists. Another aspect of interactions between species carefully considered is the description of the rate at which a predator kills a prey. Gause recognized that the kinds of predator–prey dynamics in the microcosms could not have been produced by the classic description of the interaction used by Lotka. Thus, the notion of a functional response (without that name) is introduced on page 133 that is qualitatively similar what is now known as a Type II response, but using a different functional form. Still another modern insight is the emphasis on the importance of taking a stochastic viewpoint (e.g. page 124–125) when trying to understand a predator–prey system in a more natural, complex environment. Rather than including all the factors in our understanding and model, Gause advocates including uncertainty. He emphasizes that adding stochasticity does not make necessarily lead to small changes in the theory, but in reality produces a fundamentally different theory. An intriguing aspect of The Struggle for Existence is the attempt throughout to connect the questions asked and the results of the investigations to natural systems. In fact, the second chapter sets up the problem of species persistence by focusing on natural systems. Then, in the chapters on microcosms, Gause continues the underlying theme he introduces in the first chapter of using fundamental processes by illustrating the processes that emerge from experiments by referring to natural systems. This aspect is particularly important for overcoming the argument that microcosms do not tell us about natural systems. So what would be most different if The Struggle for Existence were written today? Perhaps the most striking potential difference is illustrated by comparison with the volume written by Cushing et al. [2] about Tribolium. Gause did not use careful statistical approaches to compare his experiments to models, as these techniques were not available. It is recent developments in the use of time series approaches (e.g. [4]) that explicitly include both nonlinearities and uncertainties that will enable ecologists to go much further in answering some of the fundamental questions introduced by Gause. Strikingly, however, many of the questions central to ecology today were first Corresponding author: Alan Hastings (amhastings@ucdavis.edu). Update TRENDS in Ecology and Evolution Vol.19 No.2 February 2004 64