Sexual reproduction is a fundamental aspect of life. It is defined by the occurrence of meiosis and the fusion of two gametes of different sexes or mating types. Genetic mechanisms for the determination and differentiation of the two sexes are diverse and evolutionary labile. This book synthesizes the contemporary literature on patterns and processes of sex determination evolution. The first chapter introduces definitions and concepts of sexual reproduction. Chapter 2 provides a comprehensive classification of sex-determination systems and describes the diversity of sexual cycles across eukaryote lineages, from excavates to mammals. Subsequent chapters detail the molecular mechanisms and quantitative genetics of sex determination (Chapters 3 and 4), examine the processes of sex-chromosome evolution (Chapter 5), and discuss life-history consequences of sex-determination systems (Chapter 6). The final chapter addresses the evolutionary processes responsible for the diversity and turnover in sex determination (Chapter 7). The book provides an overview of different sex-determination systems and details of its molecular regulation in fungi, plants, and animals, many of which are covered in separate text boxes and figures. It is argued that sex determination and primary sex differentiation cannot be regarded as separate processes and that the traditional dichotomous view of genotypic (GSD) and environmental (ESD) sex determination is no longer accurate. Ample documentation is provided about how sex determination affects, and is affected by, various forms of sexual conflict, sexual selection, and speciation. The book makes clear that sex-determination evolution will remain a highly dynamic field of research in the future.
