Marine Metapopulations

While the title of this book ‘Marine Metapopulations’ is mellifluous and rolls easily off the tongue, the application of metapopulation theory to marine organisms is a less graceful match. Levins’ (1969, 1970) original theory of metapopulations examines a balance between extinction and recolonization rates of local patches that are connected by dispersal. In an attempt to minimize the threat of extinction to species living within increasingly fragmented terrestrial ecosystems, many ecologists and resource managers have evoked the concepts inherent in metapopulation ecology. However, in the marine realm, it remains unclear whether habitat fragmentation is a major threat to the many ecosystems present that have evolved within the constraints of a naturally fragmented world, and how a metapopulation concept could be applied to conservation efforts. Relatively few marine taxa experience extinctions on ecological time scales, in part due to high population connectivity conferred by planktonic larvae. Thus, most authors in this volume relax the extinction requirement to better examine their own system within a metapopulation framework. The theory of marine metapopulations is nascent still, and empirical evidence of its utility is just now surfacing. Prior to the publication of Marine Metapopulations there have been three primary texts in the field: Metapopulation Biology: Ecology, Genetics, and Evolution, Hanski and Gilpin (eds) (1997); Hanski’s sole author text, Metapopulation Ecology (1999); and the most recent Ecology, Genetics and Evolution of Metapopulations, Hanski and Gaggiotti (eds) (2004). These books clearly establish the place of metapopulation ecology within the broader fields of ecology and evolution, and provide ample evidence, both theoretical and empirical, of the applicability of metapopulation concepts in terrestrial ecosystems. However, across all three of these texts, there is a dearth of examples from the marine environment. Marine Metapopulations by Jacob Kritzer and Peter Sale begins to remedy this situation by introducing metapopulation theory across a diversity of marine ecosystems and organisms. The book contains 16 chapters from 29 contributors, including a laudatory forward by Joan Roughgarden. Following the introduction, the chapters are grouped into sections, first by taxon, with three chapters on fishes, five chapters on invertebrates, and two chapters on marine plants (seagrasses and kelp). The book ends with a ‘Perspectives’ section containing five synthetic chapters addressing conservation, genetic approaches, metacommunities, and the future of metapopulation science. The authors wrote about systems they knew well, and, in most chapters, provided a good reference list of previous work in that field, especially for studies done after 2000. The chapters include a wealth of compendium tables and useful conceptual diagrams that review or illustrate metapopulation principles. The first chapter provides historical context for the development of metapopulation theory, explaining the emergence of metapopulation ideas from marine ecological studies on settlement, recruitment, dispersal and connectivity, and from conservation imperatives. Most remaining chapters start with a nod to the classic Levins definition of a metapopulation and progress rapidly to the ‘contemporary’ definition in which extinction is unlikely. The majority of chapters review the relationship between a particular taxon and metapopulation theory, following a similar format wherein the authors review the relevant literature, discuss their definition of a metapopulation, justify that definition based on the natural history of the organism or phylum under consideration, and present case studies illustrating or contradicting the match between metapopulation theory and their taxon. The chapter on estuarine and diadromous fish metapopulations stands out as exceptionally well organized, well researched, and well contextualized in the theories of ecology and fisheries science. The sometimes vague concept of a metapopulation is clarified by (i) clearly defining ‘population’ and ‘local population’, (ii) describing a continuum of adherence to the definition of metapopulations for marine species, (iii) recognizing a distinction between naturally evolved and fragment-induced metapopulations, and (iv) choosing and describing appropriate methods (population genetics and tagging) to answer questions at different temporal scales (evolutionary and ecological). Undoubtedly, this clarity is assisted by the tidy fit between anadromous fish and metapopulation theory. Marine Ecology. ISSN 0173-9565