Abstract: This book is an edited compendium of twenty chapters addressing the evolution, adaptive significance, and genetic and developmental basis of differences between the sexes in body size and morphology. General concepts and methodologies are introduced in Chapter 1, which also includes an overview of variation in sexual size dimorphism (SSD) with emphasis on extreme dimorphisms (i.e., dwarf males) and taxa not covered in subsequent chapters. Chapters 2-7 present new, comprehensive, comparative analyses of broad-scale patterns of SSD in mammals, birds, reptiles, amphibians, spiders, and insects, respectively. Chapters 8-15 comprise case studies of SSD within species or groups of closely related species. Flowering plants, insects, lizards, birds, and mammals are represented in this section. Chapters 16-20 emphasize proximate mechanisms underlying SSD and include theoretical explorations of anisogamy, genomic conflict, genomic imprinting, sex-linkage, and sex-specific gene expression, as well as experimental studies of sex-specific patterns of growth and development. Throughout the book, the emphasis is on testing hypotheses concerning the evolution and adaptive significance of SSD, and the importance of sexual selection on male size emerges as a common theme. However, this adaptationist approach is balanced by studies of proximate genetic, developmental, and physiological processes.

Keywords: adaptive significance, body size, evolution, genomic conflict, genomic imprinting, sexual selection, sex-specific gene expression