Cover -- Half title -- Title -- Copyright -- Dedication -- Contents -- Preface -- The Phenomenon of Dual Sexuality -- Hermaphroditism in Fiction -- Hermaphroditism in the Real World -- ONE : Two Sexes in One -- Maleness and Femaleness -- Anisogamy and the Separate-sex Condition -- Evolutionary Origins -- Evolutionary Ramifications -- Sex Ratios in Separate-sex Taxa -- Relationship to Sexual Selection and Mating Systems -- Impact on Demographic Parameters -- Sex Ratios in Hermaphroditic Taxa -- Hermaphroditism Versus Separate Sexes -- Fitness Considerations -- Mating Systems and Related Phenomena -- Sex Allocation -- Phylogenetic Legacy Versus Contemporary Adaptive Significance -- Summary -- TWO : Dual-sex Plants -- Terminology -- Alternative Sexual Systems: Natural History and Examples -- Hermaphroditism -- Monoecy -- Andromonoecy -- Gynomonoecy -- Gynodioecy -- Androdioecy -- Trioecy -- Sex-changers -- Dioecy -- Cosexuality Versus Dioecy -- Ecological Considerations -- Phylogenetic Character Mapping -- Transitional States -- An Evolutionary Enigma -- Selfing Versus Outcrossing -- Inbreeding -- Coadapted Genotypes -- Fertilization Insurance -- Sex Allocation -- Sexual Selection in Plants -- Summary -- THREE : Dual-sex Invertebrates -- Biological Examples -- Reef-building Corals -- Love-dart Snails, Earthworms, and Sea Slugs -- Sperm-storing Freshwater Snails -- Sex-changing Limpets, Isopods, and Polychaetes -- Androdioecious Clam Shrimps and Gynodioecious Sea Anemones -- Protandric Simultaneously Hermaphroditic Shrimps -- Quasi-asexual Flatworms -- Other Oddities -- Sex Determination and Pseudohermaphroditism -- Evolutionary Histories: Gonochorism and Hermaphroditism -- Phylogenetic Character Mapping -- Gynodioecy and Androdioecy -- Genetics -- Selective Pressures -- Selfing Versus Outcrossing -- Genetic Considerations.

Ecological Considerations -- Joint Genetic and Ecological Considerations -- Sex Allocation in Simultaneous Hermaphrodites -- Selfing and Allocation to Female Function -- Stress and Allocation to Male Function -- Local Mate Competition -- Local Resource Competition -- Brooding Constraints -- Intra-individual Trade-offs -- Sexual Conflicts -- Other Factors -- Sex Allocation in Sequential Hermaphrodites -- The Size-advantage Hypothesis -- Mating Systems -- Conclusions About Sex Allocation Theory -- Sexual Selection -- Summary -- FOUR : Dual-sex Vertebrates -- Sexual Flexibility -- Evolutionary Lability -- Ontogenetic Plasticity -- Sequential Hermaphroditism -- The Cast of Players -- Evolutionary History -- Adaptive Significance of Alternative Modes -- Simultaneous Hermaphroditism -- The Cast of Players -- Evolutionary Constraints -- Mating Behaviors in Outcrossers -- Self-fertilization -- History of Genetic Research on the Mangrove Rivulus -- Adaptive Significance of Selfing -- Summary -- Glossary -- References Cited -- Index.