It is well known that tropical forests and savannas house a significant proportion of global biodiversity. However, an appreciation of the diversity of interactions among organisms in tropical ecosystems is only just emerging. Interactions among species are important because they affect the growth, survival and reproduction of individuals, but also because they have a key role in structuring communities and in the functioning of ecosystems. A sound knowledge of these interactions is therefore fundamental to understanding how tropical ecosystems work, as well as informing important practical concerns such as conservation, management and carbon sequestration. The aim of this book, and the meeting from which it derives, is to synthesize the current state of knowledge of biotic interactions in terrestrial communities in the tropics. Each of the 22 chapters of this volume provides a review or a case study of interactions among organisms from tropical ecosystems, with a perspective drawn from the organisms and sites with which the individual authors work. Our aim was to draw on research conducted in both Old and New World tropics and to include biotic interactions among taxa at all trophic levels. Most authors have taken plants (typically trees) as their starting point, but taken together the chapters consider interactions of plants with other plants, with micro-organisms and with animals, and the inter-relationships of human-induced disturbance with interactions among species.