Dispersal: from bacteria to vertebrates


Bullock, J.M., Kenward, R.E. & Hails, R.S. (eds) (2002) Dispersal Ecology. The 42th Symposium of the British Ecological Society. Blackwell Science Ltd, Oxford. xvii + 458 pp, figs, tables, index. Hardback: Price £59.95. ISBN 0-632-05876-5. Paperback: Price £29.95. ISBN 0-632-05877-3.

Dispersal is one of the most exciting and expansive research topics in ecology today, attracting scientists from a variety of different fields, spanning from population genetics to global change modelling. This diversity of research in dispersal ecology is the subject of a book based on a BES symposium organized by Bullock et al. in spring 2001, aimed at providing a ‘broad overview of dispersal … in all areas of ecology and covering the range of taxa from microbes to vertebrates’. Does the book achieve this ambitious aim? Both yes and no. The book contains an impressive array of dispersal-related research problems, and for readers familiar with only one or a few of these, a broadening of one's view of dispersal ecology is guaranteed. The unavoidable side-effect is that the book lacks a clear focus, and that the style and level of the 21 chapters are highly variable. The content of the book may seem confusing at first, and so does the organization of the chapters. I found the five first chapters, devoted to methodological issues, somewhat frustrating. If I were a student looking for inspiring ecological problems, I would probably become discouraged by reading about all the difficulties of studying dispersal, before having been introduced to the more interesting scientific problems. It is also an odd choice that the methodology section allocates a lot of space to well-known methods such as mark-recapture and different tagging techniques, while lacking a chapter focusing on recent developments in the use of molecular markers.

The second part of the book concerns behavioural and evolutionary ecology and includes some excellent chapters. A lack of focus is most obvious here, but each of the five chapters provides both entertaining and thought-provoking reading about issues as diverse as the ecology of passively dispersed small insects (Compton), seed dispersal trade-offs (Thompson et al.) and dispersal of genetically modified baculoviruses (Dwyer and Hails). A chapter by Okamura and Freeland synthesizes genetic and ecological information (on aquatic invertebrates) in analyses of dispersal effects on evolution and distribution patterns. This chapter illustrates nicely the value of studies that move across a range of different spatial and temporal scales.

The five chapters in the third section of the book reflect the recent rise in interest in landscape ecology. The chapter by Andreassen et al. shows how detailed monitoring of dispersal behaviour in mammals can be built into complex population models. However, in order to parameterize the models, these small mammals have to be monitored with great precision. For students of the more elusive dispersal of seeds, spores or small insects, alternative model approaches have to be developed. Three of the chapters in this section (on bacteria by Bailey and Lilley, on butterflies by Wilson and Thomas, and on plants by Bullock et al.) provide insight into such alternatives by showing many other ways to infer dispersal, in situations where exact knowledge is hard to achieve. These chapters are very well structured, balanced and informative overviews of dispersal in a landscape context. The three chapters together are as close as one gets to a coherent part of the book, and they should be essential reading for students of spatial ecology, irrespective of preferences for study organism. In contrast, the last chapter in the section, on biogeography and ecology, is disappointing — with its lack of recognition of recent developments (e.g. the use of molecular data to infer the history of geographical ranges) and poor coverage of the literature.

The fourth section of the book, devoted to applications, contains chapters that give examples of areas in which the development of a good understanding of dispersal is imperative. However, just as the book suffers from a lack of inspiration at the start, the ending parts are also slightly mundane. The chapter by South et al. (on methodology in studies of vertebrates) would have benefited from being integrated with Chapter 3, by the same authors. The applied topics covered in the final section, for example invasions and the effects of climate change, are represented by well-written chapters, although they do not provide much in the way of new thoughts or ideas.

So what have we learned from this book? First of all, dispersal is (and deserves to be) a central topic in ecological research. Future development in dispersal research will (and must) proceed along many different lines of enquiry. The book illustrates the point that integration between studies performed on different spatial scales, and in different systems, is badly needed. The aim to cover many different groups of organisms should be acknowledged, and one of the main strengths of the book is that it may inspire students focusing on organisms other than mammals, insects and plants to focus on dispersal as a key concept. The excellent chapters in the two mid sections (i.e. about half the volume) will provide thought-provoking reading for both students and researchers interested in dispersal ecology.