© 2006 Society of Systematic Biologists
Biogeography: An Ecological and Evolutionary Approach, 7th edition
Department of Systematic Zoology, Evolutionary Biology Centre, Uppsala University Norbyvägen 18D, SE-752 36, Uppsala,, Sweden E-mail: isabel.sanmartin{at}ebc.uu.se
Biogeography: An Ecological and Evolutionary Approach, 7th edition—C. Barry Cox and Peter D. Moore. 2005. Blackwell Publishing, Oxford. 428 pp. ISBN 1–4051–1898–9. £32.95 (hardback)
Much has been said and written lately about a (presumed) identity crisis in biogeography: "What is the field of biogeography, and where is it going?"(see Forum on Biogeography, Taxon 53[4]; or the last Systematics Association Biennial Meeting, Cardiff, 2005); and about the need for an integrative approach to this field (Donoghue and Moore, 2003; Riddle, 2005). This self-assessment has been triggered in part by the advent of molecular data and by the development of new methods of biogeographic analysis, challenging the old divisions of dispersal versus vicariance and ecological versus historical. In the first chapter of this 7th edition of their classic textbook, Cox and Moore define this discipline as "the study of living things in space and time ..., a multidisciplinary science related to biology, geography, geology, paleontology, and ecology" (p. 1), dealing with the questions of scale (geographic distribution, geology) and time (evolution, phylogenies), and also with an understanding of the processes and factors involved in species distributions. This definition describes well the approach of this book: a broad look at the field of biogeography, with examples drawn from a wide range of different related disciplines.
The first thing that attracts notice in this new edition of Biogeography is the substantial improvement over the previous edition. From a presentation viewpoint, there is an increase in the amount and quality of the illustrative material, with new color plates plus an attractive new cover. Parts of the text that interfered with the narrative flow in previous editions are now enclosed in useful "concept" and "methodology" boxes, which draw attention to some particular aspect of the subject and can be read independently from the main text (excepting Box 10.3). The content has also been thoroughly updated, with new references (in general up to 2003) and the inclusion of two new chapters, on molecular and isotope biogeography and on the history of biogeography.
In such a vast subject, the main challenge is to link the different elements (e.g., ecological versus historical; plant versus animal; marine versus terrestrial). The authors have managed to do this in their Introduction, where they explain the rationale for the book and the content of the chapters, but also in the brief section preceding each chapter, which links its content to that of previous chapters or to those that follow. The order of the chapters, however, is somewhat awkward. Chapters 13 and 14 on analytical methods in historical biogeography could have been placed more conveniently after Chapters 8 to 10 introducing historical biogeography, with Chapter 14 on more classic methods preceding Chapter 13 on the new molecular and isotopic biogeography. However, there is probably no single ideal order, and preference will depend on the background of the reader.
In their brilliant new Chapter 2 on the history of biogeography, Cox and Moore describe in a lively but critical way the road from Linnaeus via Darwin's theory of evolution to our modern cladistic biogeography. If anything, I am sorry that they did not go further, although Chapter 14 ("Interpreting the Past II: Principles and Practice") can be considered as a continuation of this chapter. Cox and Moore manage to portray very well the complex origin of theories and how these are influenced by the circumstances of the time (e.g., lack of knowledge, range of theories available, accepted assumptions at that time, etc.). Their warning to future students of biogeography about the dangers of accepting without questioning the current dominant theories are very accurate in this time of partisanship between dispersalists versus vicariantists and area biogeography versus phylogeography.
The following three chapters, updated from previous editions, deal with the ecological side of biogeography. Chapter 3 examines patterns of biodiversity (How many species are there? Can ecological variables explain gradients of diversity?). Chapter 4 describes different patterns of distribution and how these are limited by abiotic (environmental) and biotic (species interaction) factors. Chapter 5 finally examines different aspects of communities and ecosystem functioning (e.g., nutrient cycling).
Chapters 6 and 7 move to more evolutionary ground, with an examination of the evolutionary mechanisms that underlie biodiversity (Darwinian evolution) and the processes of evolution on islands (the Theory of Island Biogeography). A welcome addition is a new section on scientific discrepancies concerning Darwin's theory of natural selection, and how these are not the real "controversies" contended by creationists (there is an excellent Box 6.2 on the mounting evidence supporting the theory). The emphasis on the more historical-evolutionary side of biogeography is completed by Chapters 8, 9, and 10 on the larger-scale aspects of historical biogeography. Together, these chapters provide an excellent summary of the history of the climatic and geographic changes that have affected the Earth from the Late Palaeozoic to the present, and how these have influenced the distribution patterns of life. There is an excessive focus on mammalian and angiosperm biogeography, with almost nothing mentioned about other groups, but, as the authors argue, these two groups are the best known in the fossil record and represent the two extremes in dispersal abilities (they also are the two groups studied by the authors). Figure 9.1, illustrating the direction and timing of the main dispersal events in mammalian biogeography, is very informative. However, the section on angiosperm biogeography needs to be updated. The discussion of the "comparative uncertainty of flowering plant systematics" is questionable, given the recent publication of an increasing number of molecular phylogenies of angiosperms that address biogeographic questions (see Pennington et al., 2004).
Chapter 12, on marine biogeography, breaks with the natural division of ecological versus historical biogeography, but it is particularly relevant. It is now clear that ocean biodiversity is declining at a faster rate than previously predicted. Marine biogeography, however, is still at its beginnings. Oceanic regions are far more difficult to define than are terrestrial ones because of the (apparent) lack of physical barriers. Oceans themselves are also continually moving, so that long-range dispersal is much easier than in terrestrial environments. As a result, many marine species seem to be widespread in distribution, although new molecular evidence suggests that much of this could be a result of inadequate taxonomy. Most analytical methods in historical biogeography have been developed for terrestrial organisms, with their well-defined areas of distributions and patterns of horizontal endemicity. There are few applications of these methods to marine biota, partly because environmental gradients tend to be vertical, and partly because there are still few good phylogenies for marine groups. This is reflected in the mainly descriptive content of this chapter. Open-sea realm biogeography is mainly linked to ecology (light, temperature, nutrient availability); there is very little on the historical component with the exception of corals, where, because they are easily recognizable in the fossil record, historical biogeography can contribute more to understanding their patterns of distribution. Studies on shallow-sea biogeography usually involve a more historical component, but they are not always based on phylogenies. Only recently have phylogeographic methods been used to reconstruct the biogeographic history of marine groups.
The new Chapter 13 examines aspects of molecular and isotopic biogeography. It is clear that the authors are excited about the development of these recent approaches, which they believe will cast new light on many controversial areas of historical biogeography. The chapter starts with an introduction on the basic aspects of genetics and molecular biology, which will be useful for the nonbiology student, and continues with a series of interesting examples where molecular phylogenetics has revolutionized our understanding of classic biogeographic and evolutionary problems, such as the original radiation of birds in the Early Cretaceous, the history of human diversification, and the low genetic variability in cheetahs. There is also a very enlightening section on the use of isotopes to monitor climatic changes or for tracing the migration of nutrients between ecosystems.
Chapter 14, dealing with current analytical methods for historical biogeography, is the weakest chapter in the book and needs to be updated. There is a new introduction on the current divide between dispersalists versus vicariantists, and the new support from molecular phylogenies for dispersal explanations. The sections on cladistic biogeography and parsimony analysis of endemicity have been updated. However, in their review of biogeographic methods, Cox and Moore have omitted the plethora of new methods that have appeared in the last decade, in particular those born from cospeciation-coevolution studies such as reconciling trees, dispersal-vicariance analysis, maximum cospeciation, event-based methods, etc., and also the model-based methods used in phylogeography (maximum likelihood analysis, Bayesian inference). Obviously, this is not a book on methodology in historical biogeography (cf. Crisci et al., 2003), but there are other general books on biogeography that provide a better review of this subject (e.g., Lomolino et al., 2005).
The last chapter ("Foretelling the Future") is particularly interesting (and slightly depressing). Biogeography should, ideally, be a predictive science. Understanding the ecological and historical causes of present distribution patterns can help us to predict how floras and faunas will respond to climatic change, and thus help us to conserve their biodiversity. What clearly emerges from this chapter, however, is that prediction is not easy because many different factors are involved, and, despite the great volume of scientific information available, foretelling the future still remains very speculative. For example, models aiming to predict the response of a species to climate change should take into account not only physiological requirements (environmental variables) but also the history of the group and its interaction with species. When faced with climate change, recent studies have shown that ecosystems like the tundra are surprisingly resilient to environmental change.
Does the book manage to integrate the different aspects of biogeography? It is still more biased towards ecology than towards the evolutionary perspective, showing a conspicuous lack of phylogenies among the illustrations (probably reflecting the academic background of the authors). But there is clearly more about evolution than there was in previous editions, and one can expect the book to continue improving on this subject in subsequent editions. Cox and Moore take a neutral, sensible position in the ongoing debate about dispersal versus vicariance, and argue against the artificial boundaries between ecological and historical biogeography. However, the book fails to mention (probably because they were published after the book's completion) some recent attempts to truly integrate the two aspects of biogeographic research: ecological (environmental) versus historical (phylogenetic) (Wiens and Donoghue, 2004). For example, under the theory of phylogenetic niche conservatism, new studies have been published that try to integrate phylogenetic hypotheses and environmental niche models, in order to explore speciation mechanisms in organisms (Graham et al., 2004) or to explain the origin of species richness gradients (Wiens, 2004).
All in all, Cox and Moore have written an enjoyable, very readable book, which jumps easily from one subject to another, supported by a plethora of instructive, well-chosen examples. The importance of understanding biogeographic patterns for conserving biodiversity is a pervasive theme throughout the book, which makes it relevant in these times of species loss. Perhaps an over-reliance on examples is a weakness of the book, as there is a lack of emphasis on methodology. The examples read better as a narrative, and students who want to learn more about the methods used should consult the original studies. One solution could be to provide more "methodology" boxes like Box 14.1, describing the analytical methods employed in more detail. On the other hand, the summary of the works of others is what makes the reading so interesting, and the numerous literature references for each chapter provide a starting point for those who want to go further. This makes Biogeography a book appropriate not only for the uninitiated student, but also for the scientist who wants to know what is going on in the field of biogeography.
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Crisci J. V., Katinas L., Posadas P. Historical biogeography: An introduction (2003) Cambridge, Massachusetts: Harvard University Press.
Donoghue M. J., Moore B. R. Toward an integrative historical biogeography. Integr. Comp. Biol. (2003) 43:261–270.
Graham C. H., Ron S. R., Santos J. C., Schneider C. J., Moritz C. Integrating phylogenetics and environmental niche models to explore speciation mechanisms in dendrobatid frogs. Evolution (2004) 58:1781–1793.[Web of Science][Medline]
Lomolino M. V., Riddle B. R., Brown J. H. Biogeography (2005) 3rd edition. Sunderland, Massachusetts: Sinauer Associates.
Pennington R. T., Cronk Q. C. B., Richardson J. A. Introduction and synthesis: plant phylogeny and the origin of major biomes. Phil. Trans. Roy. Soc. Lond. B Biol. Sci. (2004) 359:1455–1464.
Riddle B. Is biogeography emerging from its identity crisis? J. Biogeogr. (2005) 32:185–186.[CrossRef]
Wiens J. J. Speciation and ecology revisited: Phylogenetic niche conservatism and the origin of species. Evolution (2004) 58:193–197.[Web of Science][Medline]
Wiens J. J., Donoghue M. J. Historical biogeography, ecology and species richness. Trends Ecol. Evol. (2004) 19:639–644.[CrossRef][Medline]
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