The study of mutualism

Abstract Mutualisms, interactions between two species that benefit both of them, have long captured the public imagination. However, the importance of mutualisms lies much deeper than simply providing material for philosophical treatises and endless natural history documentaries: their influence transcends levels of biological organization from cells to populations, communities, and ecosystems. In light of our deeply ingrained fascination with their natural history and their more recently recognized ecological and evolutionary importance, it is surprising how little conceptually oriented literature on mutualism yet exists. This chapter introduces the themes covered in this volume as a whole, while focusing on how mutualism has been and currently is being defined and studied. It first addresses semantic issues. How can the universe of interactions between species be divided up, and then how do we define and group the mutually beneficial ones? The terminology used throughout the volume is summarized, and then the history of mutualism studies is reviewed. While we have long had a surprisingly deep knowledge of many individual mutualisms, a synthetic and conceptual perspective on mutualism as a whole was much slower to develop. Mutualism as a discipline has now taken off, as will be evident in the subsequent chapters of this book.