Introduction: the enigma of sexual size dimorphism This
introductory chapter opens by describing general patterns of
variation in sexual size dimorphism (SSD), with emphasis on
several taxa (plants, fishes, and aquatic invertebrates) not
included in the survey chapters that follow. It also highlights
recently documented examples of extreme SSD, such as Lamprologus
callipterus, a shell-brooding cichlid fish, where males are >12
times heavier than females, and the blanket octopus (Tremoctopus
violaceous), where females can be 40,000 times larger than the
dwarf males. The chapter then develops the two major integrative
themes of the book: discovering the adaptive significance of SSD
and determining the importance of genetic constraints in shaping
its evolution. After briefly summarizing the contributions of
the chapters to these themes, the chapter closes by discussing
methodological difficulties associated with estimating adult
body size and SSD in natural populations. Oxford Scholarship
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