Over the last two decades, the study of speciation has expanded from a modest backwater of evolutionary biology into a large and vigorous discipline. Thus, the literature on speciation, as well as the number of researchers and students working in this area, has grown explosively. Despite these developments, there has been no book-length treatment of speciation in many years. As a result, both the seasoned scholar and the newcomer to evolutionary biology had no ready guide to the recent literature on speciation–a body of work that is enormous, scattered, and increasingly technical. Although several excellent symposium volumes have recently appeared, these collections do not provide a unified, critical, and up-to-date overview of the field. Speciation is designed to fill this gap.Aimed at professional biologists, graduate students, and advanced undergraduates, Speciation covers both plants and animals (the first book on this subject to do so), and deals with all relevant areas of research, including biogeography, field work, systematics, theory, and genetic and molecular studies. It gives special emphasis to topics that are either controversial or the subject of active research, including sympatric speciation, reinforcement, the role of hybridization in speciation, the search for genes causing reproductive isolation, and mounting evidence for the role of natural and sexual selection in the origin of species. The authors do not hesitate to take stands on these and other controversial issues. This critical and scholarly book will be invaluable to researchers in evolutionary biology and is also ideal for a graduate-level course on speciation.