Review by Barry Brook (Key Centre for Tropical Wildlife Management, Northern Territory University Darwin, Northern Territory, Australia) in Austral Ecology (2002) Vol 27.

Like it or not, contemporary ecologists and conservation biologists need to understand genetics. The managers of the Greater Prairie Chicken will attest to this fact. The size of the remnant Illinois population declined from more than 25 000 in 1933 to 2000 in 1972 and <50 by 1992. The initial threat was clearly a loss and fragmentation of habitat, but later, a concurrent decline in genetic diversity and reproductive fitness was documented. Despite intensive conventional management efforts (habitat restoration) targeted at arresting the original cause of the decline, the species continued to plummet towards extinction. It was only when genetically prescribed conservation measures were tried (translocations of unrelated birds from large, genetically diverse populations) that reproductive fitness and, subsequently, population size began to recover. This case study, and many others described in Introduction to Conservation Genetics, highlights the critical need to understand genetic factors when attempting to manage and recover threatened species.

Unfortunately, until ecologists actually study some genetics, or at least some case studies where genetics have played a major role, they tend to remain blissfully (or willfully) ignorant of its potential importance to them. For instance, although it is widely accepted that species in natural habitats face the threat of extinction from both deterministic factors (e.g. habitat loss, over exploitation, pollution and introduced species) and stochastic hazards associated with small population size (e.g. demographic and environmental fluctuations and catastrophes), genetic threats (inbreeding depression, loss of genetic diversity and mutational accumulation) have a long history of being dismissed as unimportant. Introduction to Conservation Genetics provides, among other things, a compelling and up-to-date critique of this widely-held viewpoint.

The book begins with its leading punch, setting the context for conservation genetics in the big picture (i.e. the current biodiversity crisis) and providing a succinct overview of the critical interactions between genetics and extinction. Once you're hooked, the remainder of the book draws you in to the theory, evidence and methods that lie behind the science of conservation genetics through extensive reviews of the literature and the authors' own work. The text (more than 600 pages organized into 20 chapters in three sections) is highly readable yet concise and full of interesting case studies, examples, problem exercises and marginal focus boxes designed to hammer home the main points. In addition, the book is copiously illustrated with beautiful pen and ink portraits of the threatened species being discussed, which brings the subject matter to life.

Section I is essential reading for those not familiar with the fundamental principles of population and evolutionary genetics. Of particular interest is the contrast provided between evolutionary processes in large versus small populations (chapters 6-8). In large (i.e. most non-threatened) populations, adaptation through natural selection prevails. However, in small (i.e. threatened) populations, random processes such as genetic drift and mutational accumulation become the predominant evolutionary forces. This disturbing fact needs to be borne in mind when arguing for the preservation of so-called 'locally adapted' subpopulations with no other justification than that they show genetic differentiation.

Section II gets to the heart and soul of conservation genetics: the genetic implications of population size reduction. Inbreeding is the most immediate and potentially damaging of these. By drawing on a wealth of laboratory, zoo and field studies, the authors demonstrate that essentially all well-studied naturally outbreeding species show depressed reproductive fitness in inbred individuals and that this increases their vulnerability to extinction. Further, rather than treating genetics in isolation, they underscore the important interactions between the impacts of inbreeding and both deterministic factors and 'nongenetic' stochastic factors (summarized in chapter 20), highlighting the patent absurdity of treating these factors in isolation.

Section III is perhaps of most interest to ecologists, as it describes the myriad of really useful genetic methods now available, which have the potential to provide answers to otherwise unresolvable ecological and taxonomic questions. For instance, dispersal rates can be notoriously difficult to estimate in wild conditions because of the often enormous logistical demands and small sample sizes associated with radiotracking or mark-recapture methods. Molecular genetic analyses, on the other hand, can provide many of the same answers, yet do so more rapidly, at much reduced cost, with minimal disturbance to the organism or habitat and with the additional benefit of illuminating the broader evolutionary theatre within which all conservation and management priorities should ideally be evaluated. It also provides a framework for making sense of contemporary debates regarding the real-world application of biotechnology, such as the detection and environmental impact of genetically modified organisms.

Where does this new book sit in relation to other authoritative works in this field? The discipline of conservation genetics came of age in the early 1980s with the publication of Conservation and Evolution (Frankel & Soulé 1981). Subsequently, with an explosion of interest in both the genetic and non-genetic components of species endangerment, and their interaction, there has been a proliferation of work in this field. A number of recent edited books (e.g. Conservation Genetics Case Studies from Nature ; Avise & Hamrick 1996) present advanced treatments of cutting-edge techniques and topics. However, Introduction to Conservation Genetics provides the first teaching text specifically designed to open up conservation genetics to 'the masses'. The target audience is advanced undergraduates, postgraduates, wildlife managers and professional biologists largely unacquainted with genetics.

My reviewing this book may appear somewhat nepotistic; after all I did my postgraduate training under the supervision of the first author (Dick Frankham), took an undergraduate genetics course run by the second (David Briscoe), and had my thesis examined by the third (Jon Ballou)! Further, I still collaborate with all of these scientists. So why should you trust my opinion? Because irrespective of my personal biases, reading this excellent book really will make you comfortably conversant with conservation and evolutionary genetics and that's a useful weapon in any modern ecologist's armoury.