Speciation in Birds
Roberts & Co. Publishers, CO, USA; 2007. 152pp.
Review by Jim Groombridge
This book declares as one of its aims to sort out the complementary roles of geographical isolation and ecological differentiation in birds, and in this it succeeds. The author, Trevor Price, integrates modern advances in our understanding of evolutionary time (phylogenetics) alongside the more traditional disciplines of geography, behaviour and ecology in our interpretation of bird speciation. Given the obvious links that the subject of this book has with the likes of Charles Darwin and David Lack, perhaps more could have been made of this historical element, to provide a clearer picture of how this book is able to bring our understanding of bird speciation to new heights.
The book is set out in three sections that broadly cover ecology and natural selection in speciation, sexual selection and social factors, and lastly, reproductive isolation and hybridisation. Throughout each chapter, appendices on various topics provide a more in-depth summary of key topics, which works well to retain necessary detail whilst not falling into the trap of getting weighed down by technical and often controversial issues. This style ensures the text is very readable and will, I suspect, encourage a broad readership. In places, Price forces the reader to judge for themselves on various topics. For example, he offers no excuse for his widespread use throughout this book of a mitochondrial DNA rate of 2% sequence divergence per million years, beyond a brief summary of prevailing literature in the text (and from here the reader is guided to an appendix on molecular dating methods, which provides an excellent review). Whilst this approach might appear blunt to some, it draws attention to the current limit of our understanding on various topics in a thought-provoking manner.
Several chapters appear to deal with rather similar topics (for example, Chapter Two on Geography and Ecology and Chapter Three on Geographical Variation) and some lumping of chapters together might have painted a more honest picture of where the real distinctions lie amidst our understanding of bird speciation, as opposed to those portrayed by the author. Throughout the book however, points are illustrated by new data or new relationships drawn from previous studies, not simply repetitions or reproductions of previous work. This adds immensely to the novelty of the book and allows it to provide new insights about our knowledge of bird speciation rather than to simply review it. There are excellent colour figures throughout, often containing illustrations that bring examples to life. Chapter Seven on Behaviour and Ecology raises some interesting and intriguing ideas regarding forebrain size, tendency towards feeding innovation by a species and species richness across birds. This chapter in particular integrates genetic divergence alongside behavioural data to good effect, as does Chapter Ten on Social Selection and the Evolution of Song.
Price does an admiral job of uniting fundamentally different topics from diverse disciplines. He meets this challenge by pairing them up in turn, such as Sexual Selection and Ecology, Behaviour and Ecology, Ecological Controls on Speciation, and Social Selection and Ecology, and in doing so he charts a navigable route towards concise conclusions in each chapter. The final two chapters return to genetic topics (Hybrid Zones, and Genetic Incompatibility) before a general conclusion that is loyal to the books overall structure. This book is a rich treasure trove of new ideas set within a comprehensive and wonderfully illustrated treatment of the study of speciation in birds; I imagine it would meet with approval from the likes of Darwin and Lack.
Dr. Jim Groombridge is at the Durrell Institute of Conservation & Ecology, University of Kent, UK