"In this advanced work, written for an audience with a background in genetics and evolutionary biology, Mitton examines the rich and controversial body of research relating molecular variation to selection in natural populations. . .A highly useful reference on the genetic structure and evolution of populations for population geneticists, evolutionary ecologists, and physiological ecologists." --Choice"The book is well written, has a good balance of theory and fact, and the arguments are supported and illustrated by clear diagrams. It is short and enjoyable to read." --American Zoologist"Mitton summarizes many studies of protein and genetic variation, asking fundamental questions in evolutionary biology: What is the unit of selection? What role does the unit of selection play in the amount of genetic variation detected using protein electrophoretic studies versus studies that directly examine DNA? How does selection impact the structure of the genome? What generalizations can be made about heterozygosity and multilocus interaction on fitness? . . . The book is mainly a summary of empirical data. Despite years of considerable effort by evolutionary biologists, there are very few general answers to accompany the long lists of questions. . . . [T]he book . . . will probably be of interest to new graduate students in the field and will serve as an introduction to a wide range of examples and as a reference to the literature."--The Quarterly Review of Biology