There are many books on aspects of plant invasions, but none that focus on the key role of species interactions in mediating invasions. This book reviews exciting new findings and explores how new methods and tools are shedding new light on crucial processes in plant invasions. In 23 chapters, with contributions from 51 authors, the book addresses: * the main theories and hypotheses in plant invasion ecology that invoke species interactions; * plant invasions that are facilitated by, or benefit from, by mutualistic interactions and release from enemies; * antagonistic interactions that prevent or hinder plant invasions; * impacts of plant invasions on native species interactions and ecosystem functioning; * the interaction-network approach to understanding plant invasions; * the importance of considering species interactions in managing plant invasions