John C. Avise is Distinguished Professor of Ecology and Evolutionary Biology at the University of California, Irvine. He is an elected member of both the National Academy of Sciences and the American Academy of Arts and Sciences, and the author or editor of 20 books, including most recently Inside the Human Genome: A Case for Non-intelligent Design; Molecular Ecology and Evolution: The Organismal Side; and Clonality: The Genetics, Ecology, and Evolution of Sexual Abstinence in Vertebrate Animals.

• Preface The Phenomenon of Dual Sexuality Hermaphroditism in Fiction Hermaphroditism in the Real World 1. Two Sexes in One Maleness and Femaleness Anisogamy and the Separate-sex Condition Sex Ratios in Separate-sex Taxa Sex Ratios in Hermaphroditic Taxa Hermaphroditism Versus Separate Sexes Summary 2. Dual-sex Plants Terminology Alternative Sexual Systems: Natural History and Examples Cosexuality Versus Dioecy Selfing Versus Outcrossing Sexual Selection in Plants Summary 3. Dual-sex Invertebrates Biological Examples Sex Determination and Pseudohermaphroditism Evolutionary Histories: Gonochorism and Hermaphroditism Selfing Versus Outcrossing Sex Allocation in Simultaneous Hermaphrodites Sex Allocation in Sequential Hermaphrodites Conclusions About Sex Allocation Theory Sexual Selection Summary 4. Dual-sex Vertebrates Sexual Flexibility Sequential Hermaphroditism Adaptive Significance of Alternative Modes Simultaneous Hermaphroditism Summary Glossary References Cited Index

This book provides a basic, nontechnical introduction to sexual systems for a wide audience of readers. Choice Avise's book is truly what is expected from a primer, and ought to be read by all researchers interested in hermaphroditism, perhaps even more botanists than zoologists. -- Philippe Jarne The Quarterly Review of Biology Finally!...This new book, for the first time, assembles our state-of-the-art understanding of the biology of hermaphrodite gender expression, and makes the current research agenda on these fascinating organisms broadly accessible to both scientists and (under-)graduate students... -- Nils Anthes Ecology