Mutualism ed. by Judith L. Bronstein

Mutualisms are species interactions with reciprocal benefits for two or more participating species. They are diverse in form and function, and key to many important ecological processes and evolutionary transitions. Historically, mutualisms have been considered understudied relative to antagonistic interactions, such as competition and predation, which was a common refrain in the last edited volume on the biology of mutualism (Boucher 1985). In 1994, Judith Bronstein wrote a review article in which she asked if the common perception that mutualisms are poorly studied is an accurate one. Interestingly, she found that, in fact, there were many studies of mutualism; however these studies tended to focus more on descriptive natural history and system-specific observations than the more general conceptual importance of these positive species interactions to Ecology, Evolution, and Conservation. She challenged biologists to address major conceptual questions across the diversity of mutualistic interactions in order to gain a more thorough understanding of their ecological and evolutionary importance (Bronstein 1994). Twenty years after her review, and thirty years after the last synthetic edited volume on mutualisms, Bronstein gathered an impressive group of scientists to assess our progress in gaining a more thorough understanding the conceptual importance of mutualisms.

The book is organized, not by type of interaction (e.g., pollination, ant protection, etc.), but by broad concepts. In the first chapter, Bronstein sets the stage by reviewing the history of the study of mutualisms and, importantly, clarifying semantic issues regarding the terminology associated with the study of mutualism. This is no small issue, since many discussions of mutualisms rapidly dissolve into disagreements about terminology. The other chapter in the first section of the book is focused on symbiotic mutualisms. Section II addresses mutualisms in terms of their evolutionary origins, and the ways that mutualisms can influence the evolutionary trajectories of participant species. This section provides a diversity of viewpoints, from macro-evolutionary patterns to micro-evolutionary dynamics, and from theoretical models of persistence to empirical tests of model predictions. The third section of the book focuses on the Ecology of Mutualisms, from the perspective of contemporary populations, communities, and ecosystems. It also includes a chapter about context dependency and a chapter about using networks to understand the complex interactions among diverse guilds of participants in mutualisms. Finally, the book ends with a section about the effects and persistence of mutualisms in the face of global environmental change, with one chapter focused on the anthropogenic threats to mutualisms and the other addressing the progress that has been made in the fields of Conservation and Restoration Ecology to understand, and potentially ameliorate some of these effects.

One of the most impressive aspects of this volume is that it maintains a broad focus on mutualisms in general, rather than particular types of interactions, throughout most of the chapters. This approach allows readers to think broadly about general ecological themes associated with mutualisms, while still providing important information about natural history to ground these assertions in the biology of real organisms. A large part of the success of this effort can be attributed to the diversity of viewpoints represented by the authors-both of the main text and boxes. In fact, the boxes were, without exception, interesting, relevant, and well integrated into each chapter. For example, in a chapter about the population ecology of mutualisms, J. N. Holland focuses on the potential importance of modeling mutualisms as consumer resource interactions, while boxes from A. L. Laine and K. McCann describe the advances in metapopulation and phase plane models, respectively, as tools for understanding mutualistic interactions at the population level. Clear links were made between all three types of models in the text of the chapter.

There is also a nice blend of theoretical and empirical research throughout the book, with clear indications of recent advances and current research priorities. For example, in his chapter on exploitation of mutualisms, J. Sachs describes one surprising finding from the past 30 years of mutualism research-that cheater mutants are much less common...