A Primer of Ecological Genetics. Jeffrey K. Conner and Daniel L. Hartl. Sinauer Associates, Sunderland, MA, 2004. 304 pp., illus. $34.95 (ISBN 087893202X paper).
The field of ecological genetics became firmly established 40 years ago with the publication of E. B. Ford's seminal book, Ecological Genetics (1964). The work Ford described in that book represented a quarter-century of studies in which the theoretical predictions of how natural genetic systems should act were tested empirically under real field conditions. This period defined the beginning of a discipline that combined field-based ecology with laboratory-based genetics; the strategy provided unique insight into natural population-level processes.
In its modern form, ecological genetics addresses two broad aspects of biology: (1) the genetic basis of ecologically important traits and (2) the ecological and evolutionary processes that influence patterns of genetic variation in and among natural populations. Ecological genetics therefore borrows heavily from the conceptual frameworks of population and quantitative genetics, and it represents a powerful and unifying approach for understanding ecological responses and evolution in natural populations. In the four decades since Ford's book was published, the field has grown tremendously, and as genetic and genomic resources continue to be developed and applied to ecological questions, the future of ecological genetics seems especially bright.
An excellent introduction to basic conceptual and practical aspects of ecological genetics now can be found in the popular Primer series, published by Sinauer Associates. A Primer of Ecological Genetics, by Jeff Conner (professor at the W. K. Kellogg Biological Station and the Department of Plant Biology, Michigan State University) and Daniel Hartl (Higgins Professor of Biology at the Department of Organismic and Evolutionary Biology, Harvard University), covers basic population and quantitative genetic principles and explains how these approaches are applied to study evolutionary dynamics in both natural and managed populations. Clearly and concisely written, the book is geared toward advanced undergraduates, graduate students, and professionals outside the field in search of a basic introduction.
The chapters in A Primer of Ecological Genetics are logically arranged, with the ideas that are introduced in earlier chapters frequently revisited and reinforced in later chapters. Following a brief introduction to fundamental genetic concepts and terms in chapter 1, the next two chapters address basic population genetic principles of natural populations. The reader is introduced to the concept of population genetic variation, its measurement with different types of molecular markers, and the basic statistical and mathematical foundations for quantifying genetic variation within and among populations. Ecologically and evolutionarily relevant forces that influence the extent and patterning of genetic variation are considered both individually and in combination. These forces include mutation, genetic drift, gene flow, and natural selection.
Chapters 4 and 5 introduce the reader to the analysis of quantitative traits, which are traits distributed continuously as a result of their polygenic basis and environmental sensitivity. (The majority of ecologically relevant traits are quantitative traits.) The concepts of genetic and environmental sources of phenotypic variance and covariance are explained, as are methods for estimating standard quantitative genetic parameters such as heritability and correlation. Also covered are phenotypic plasticity, artificial selection, and the more recent development of QTL (quantitative trait locus) mapping, in which the approximate genomic locations of loci underlying variation in quantitative traits are determined through an analysis of their linkage to polymorphic molecular markers.
Conner and Hartl reserve the final two chapters for addressing how natural selection on ecologically important phenotypes can be measured in populations (chapter 6) and how the principles of ecological genetics can be applied to societal issues ranging from biological conservation to the fitness effects of escaped crop transgenes and the evolution of resistance in pest species (chapter 7). These final chapters represent an integration of concepts and methods covered in chapters 2–5.
As in other books from the Primer series, discussions of all concepts and principles are accompanied by examples of real data taken from the primary literature. This practice is particularly effective here, given the wide range of subjects covered. The pen-and-ink illustrations of organisms accompanying the examples provide an especially nice touch. Although familiarity with some basic statistical techniques (e.g., analysis of variance and regression) is helpful, the authors provide short introductions to such methods in stand-alone boxes for the statistically uninitiated. Each chapter closes with a short problem set testing the reader's knowledge of material covered and a list of additional suggested reading for those willing to delve deeper.
I found the authors' examinations of the strengths and weaknesses of different experimental approaches especially useful. For example, following the discussion on heritability and how it can be measured (chapter 4), the authors summarize the pros and cons of the different experimental designs for estimating this important parameter. Similarly, in chapter 6, explanations of experimental methods for measuring selection on phenotypes in natural populations are followed by caveats regarding the limitations on interpretation of the various approaches. These additional discussions will make A Primer of Ecological Genetics a valuable reference for new graduate students as they consider experimental designs and approaches in their own work.
It will be interesting to see what future editions of this title will cover, given the current surge in genome science. As genomic approaches increasingly become applied to ecological studies (Feder and Mitchell-Olds 2003, Thomas and Klaper 2004), new avenues for ecological genetic research will undoubtedly be established. Genomic methods may well deserve inclusion in future editions.
In sum, A Primer of Ecological Genetics provides a lucid introduction to foundational principles in the field. In their preface, Conner and Hartl state, “The guiding principle of the book is to focus on clear explanations of the key concepts in the evolution of natural and managed populations.” The first edition of A Primer of Ecological Genetics accomplishes this nicely. I recommend it with enthusiasm.