Metapopulations and Wildlife Conservation

Metapopulations and Wildlife Conservation. DALE R. MCCULLOUGH, ed. Island Press, Washington, D.C., 1996, x + 429 pp., illustr., index, (ISBN 1-55963457-X cloth) $55.00, (ISBN 1-55963-458-8 paper) $28.00.

Although Andrewartha and Birch (1954) recognized that animal populations exist as spatially discrete subpopulations, Levins (1970) deserves the credit for formally developing metapopulation theory. More recent investigators have realized that metapopulation theory may provide clues for preventing extinctions of native species whose habitats have been drastically reduced and increasingly fragmented by human activities. Metapopulation theory has risen to the rank of "the population paradigm of this decade" (Boyce, quoted on the book's back cover) largely due to its perceived promise for managing and conserving rare species. As evidence of this rise, a symposium on Metapopulations and Wildlife Conservation was organized by Dale McCullough at the 1994 annual meeting of The Wildlife Society. This symposium culminated in an edited volume of the same name. Metapopulations and Wildlife Conservation is sandwiched chronologically between two other recent treatments of metapopulation biology-Gilpin and Hanski (1991) and Hanski and Gilpin (1997)-but it differs from them in emphasizing not the elaboration and empirical evaluation of metapopulation theory but its relevance for wildlife managers faced with guaranteeing the long-term viability of rare animal species. Interestingly, the books share several of the same authors. McCullough addresses this volume to "an applied professional audience" with the goal "to explore how metapopulations function. . so that this knowledge can be applied to assure population persistence." McCullough has organized the book well into 17 chapters comprising two parts. The first six chapters review the conceptual framework of metapopulation theory, emphasizing recent theoretical and empirical links with mathematical modeling, population genetics, and landscape ecology. The next 11 chapters present a series of case studies that illustrate the range of metapopulation theory applications to conservation and restoration of endangered animal populations.

McCullough's introductory discussion of the history of the metapopulation concept underscores the urgency of developing effective management efforts aimed at rare species. The next five chapters include Gilpin's cogent summary of the value of spatially structured population models, Hedrick's discussion of how metapopulation dynamics may influence population genetic structure, Wiens' emphasis on the role of spatial scale and landscape complexity for animal persistence, Lidicker and Koenig's review of vertebrate responses to habitat edges and corridors, and Sjogren-Gulve and Ray's exploration of environmental heterogeneity in analyzing species' response to habitat patchiness. This first section provides a solid, comprehensible background to metapopulation theory, reviews useful techniques for analyzing metapopulation dynamics, and notes the potential pitfalls of translating ecological theory into actual management strategies.

As the title of the book indicates, the examples in the second section highlight wildlife species, but these range from four large terrestrial mammal species (cougar brown/grizzly bear, mountain sheep, and tule elk), to two marine mammals (Mediterranean monk seal and Steller sea lion), one small mammal (Stephens' kangaroo rat), and two bird species (northern spotted owl and Florida scrub jay). McKelvey and Noon's chapter on population modeling approaches, emphasizing the northern spotted owl, provides a nice transition to the second part of the book. Gutierrez and Harrison follow with a critique of the use of metapopulation theory in spotted owl management and conclude with an excellent summary of what metapopulation thinking has brought to wildlife conservation. The next eight chapters present case studies of species whose management may benefit from a metapopulation-based approach. Many of the cases usefully combine historical records of species distribution (York et al., Craighead and Vyse, Bleich et al.) with demographic and/or genetic data (Stith et al., Price and Gilpin, Harwood et al., York et al., Craighead and Vyse, Bleich et al., McCullough et al.). Some authors conduct spatial analyses using Geographic Information Systems (GIS; Stith et al., Bleich et al.) or use simulation modeling to reveal population persistence under various management scenarios (Price and Gilpin, York et al., Beier, McCullough et al.). Not surprisingly, the studies reveal that the metapopulation approach is more useful for some species than for others. McCullough concludes the volume with suggestions for future research, particularly a justified plea for studies that quantify animal dispersal in the context of landscape spatial structure.

A recurring question throughout the book is, to what extent can metapopulation theory be directly applied to conservation and management of wildlife populations? McCullough's intent is not to discuss whether certain species exhibit the dynamics of "pure" metapopulations (theorists can quibble about that), but to mandate a broader, "landscape" perspective for wildlife management and conservation. Some contributors espouse McCullough's liberal interpretation of the metapopulation concept, focusing on the general phenomenon of animals in habitat patches separated by some distance and the need to consider such spatial structure in managing those populations. Others exert caution in applying the theory, stressing the importance of considering the specific assumptions of metapopulation theory in devising plans for population management. For example, Wiens (Ch. 4) advises, "If we are to expect the theoretical predictions of metapopulation persistence to apply to real-world populations, the underlying conditions of the theory should be satisfied." While the contributing authors vary in their perspectives, all would likely agree that effective management schemes must look beyond local populations or nature reserves to the regional scale and consider the implications of activities among, rather than just within, habitat patches.