Is it possible to omit parasites when studying free-living organisms? The answer is clearly no! Parasites have evolved independently in numerous animal lineages, and now make up a considerable proportion of the biodiversity of life. Ecologists, epidemiologists, conservationists and evolutionary biologists are increasingly aware of the universal significance of parasites to the study of ecology and evolution where they have become a powerful model system. This book provides a summary of the issues involved as well as an overview of the possibilities offered by this research topic including the practical applications for disease prevention. It uses well-documented case-studies across a range of scales to illustrate the main trends and prospects in this area, outlining areas for future research. Ecology and Evolution of Parasitism is the first book to provide a broad synthesis of both the roles and consequences of pathogens on the ecology and evolution of free living systems.It focuses on hosts rather than the parasites themselves, integrating those aspects related to the ecology and the evolution of free-living species (sexual selection, behaviour, life history traits, regulation of populations etc. ). The book includes examples across a range of scales from individuals to populations, communities and ecosystems.