The Study of Mutualism, Past, Present, and Future*

After a fitful start, the conceptual study of mutualism (mutually beneficial interspecific interactions) is now flourishing. In 1994, I reviewed the status of the field as reflected in the peer-reviewed literature; I also laid out directions for future research. Here, I look back on that assessment and offer an updated perspective on our understanding of mutualism. Most of the open questions I identified now have significant literatures of their own. New questions have sprung from each of these, and methodological innovations have made it more possible than ever before to obtain answers. I identify one astonishing gap from 1994: the absence of attention, either in journals or in my own synthesis, to the fate of mutualisms in a changing world. I offer a brief assessment of the now-massive literature on this topic. Finally, I suggest some directions in which the field as a whole might profitably move in the future.