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Invasive Exotic Species in the Sonoran Region . Tellman, B. , editor . 2002 . The University of Arizona Press , Tucson . 460 pp . $75.99 ( hardcover ). ISBN 0-8165-2178-6 .

This multiauthor volume is an invaluable resource for both professionals working on various aspects of conservation of the indigenous flora and fauna of the Southwest and informed nonprofessionals interested in conservation. It provides comprehensive coverage of the occurrence of exotic species in the Sonoran region, the effects of these species on native biota, and possibilities for their control. The volume is a treasure trove of information on naturalized and exotic species and covers both flora and fauna. The two appendices for the flora and fauna, respectively, listing naturalized and exotic species in the Sonoran region, are particularly useful.

The volume is organized into three sections: a broad perspective on the introduction and spread of exotic species, a comprehensive treatment of the exotic species in different areas of the Sonoran region, and a section on the management of certain exotic species. In the section of the book dealing with the broad perspective, Van Davender's chapter provides a geologic time scale for the evolution and dispersal of plants and animals and explores natural changes in species distributions. Tellman discusses the historical colonization and dispersal of exotic species by humans throughout the Southwest. Case studies of exotic plant and animal species, such as saltcedar (tamarisk [Tamarix spp.]) and honeybee (Apis mellifera), also are provided.

McLaughlin uses a novel approach to make the point that the dramatic increase of exotic species in the published records of local floras of the western United States, from the 1900s to the present, reflect human impacts. Another interesting trend is the decline of exotic species with increased elevation. He demonstrates, convincingly, that low-elevation regions have the greatest numbers of exotic species and argues that most exotics come from temperate regions of Europe, Asia, or the Mediterranean. Several chapters address the impact of exotic species on grasslands, including an interesting chapter on the effects of Bufflegrass (Pennosetum ciliare) on Mexican grasslands (Burguez-Montijo).

Although most chapters focus on invasive plants, the impacts of exotic vertebrates also are covered. Mellink gives an overview of exotic reptiles, birds, and mammals on the islands of the Sea of Cortez. Rosen and Schwalbe provide case studies of the impacts of exotic reptiles and amphibians on native species and make recommendations for their control. Stevens and Ayers discuss the impact of exotic species on native fishes of the Grand Canyon.

Several chapters deal with methods to control or limit the spread of exotic species and evaluate their effectiveness (e.g., Bock & Bock, Rutman & Dickson, Tellman). Biological control is especially favored because of its high specificity and low cost (Gould & Deloach). Several examples of biological control of weeds in the Sonoran region are provided (e.g., control of puncturevine [Tribulus terrestris] by two species of weevils). Many authors also emphasize the need to involve the public in the control of exotic species, through education and active involvement.

The complexity of issues surrounding the impact of exotic species on the native biota is illustrated with studies of saltcedar. Saltcedar apparently has a substantial impact on plant and animal diversity in disturbed habitats (Stevens & Ayers) but a negligible impact in relatively undisturbed habitats (Stromberg & Chew). These two studies suggest that the effect of exotic species on native biota depends on many abiotic as well as biotic factors.

Overall, this book is a comprehensive and informative treatment of the impacts of exotic species at various scales, from ecosystems and communities to individual species. It provides a realistic assessment of the magnitude of the problem, and leaves the impression that this is a complex issue with no easy solution.