Adaptive Radiation

by

Rosemary G. Gillespie, Christine E. Parent

• LAST REVIEWED: 13 January 2014
• LAST MODIFIED: 13 January 2014
• DOI: 10.1093/obo/9780199941728-0004

Introduction

Adaptive radiation, defined as the evolution of ecological diversity within a rapidly multiplying lineage, can be considered the linchpin that unites ecology with evolution and is central to understanding evolutionary processes overall. With their remarkable species richness, which is often accompanied by striking morphological diversity, adaptive radiations are the ultimate showcases of evolution through natural selection. Many adaptive radiations are found in discontinuous habitats, where lineages have diverged and multiplied in a replicate manner down a chain of islands, lakes, mountaintops, plant hosts, and so forth. The radiating lineages are often much more diverse in their ecological functions within the ecosystem than their closest less diverse relatives. The remarkable phenotypic and ecological diversification characteristic of adaptive radiation has long intrigued scientists, who have described the phenomenon for many lineages and are now just beginning to understand its underlying mechanisms. Because most cases of adaptive radiation in nature necessarily unfold over extended time periods, scientists have relied extensively on comparative and inference methods to deduce its evolutionary and ecological underpinnings.

General Overviews

The question of why and how a single lineage evolves to become a series of slightly modified versions of its ancestor, often with each variant filling a correspondingly different role and/or space in the ecological landscape, formed one of the primary examples in the theory of natural selection published in Darwin 1872 and remains of great scientific interest. The first development of a clear theoretical framework to study adaptive radiation can be traced back to the Modern Synthesis, with significant contributions from Lack 1983, Simpson 1984, and Simpson 1953. The following forty years or so were marked by the accumulation of putative cases of adaptive radiations with detailed description of patterns of phenotypic divergence in explicit geographical space. The study of adaptive radiation was further stimulated with the advent of molecular tools to infer species relationships independent of morphological similarity, and the potential to reconstruct not only species ancestry but also ancestral traits and geographical distributions. Givnish and Sytsma 1997 provides a collection of chapters representing the burgeoning of methodological approaches triggered by molecular data. Schluter 2000 is currently the most up-to-date and complete synthesis on the “ecological theory” of adaptive radiation; rather than looking at broad-scale patterns, the book examines recent evolutionary events so as to understand mechanisms involved. In addition to publications presenting a general overview on the subject, several books have focused on a single study system to examine the evolutionary patterns and processes of diversification in the context of adaptive radiation. Peter and Rosemary Grant have dedicated their scientific careers to the study of Darwin’s finches, certainly one the best-known cases of adaptive radiation. Grant and Grant 2008 presents a detailed overview of the authors’ findings and is a very accessible book for anyone interested in the topic. Another lineage-specific book worth the attention of students and researchers alike is Losos 2009 on the radiation of Anolis lizards in the Caribbean. Both publications are excellent illustrations of the integrative nature of the study of adaptive radiation.

• Darwin, Charles. 1872. On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 6th ed. London: John Murray.

  Darwin’s original work introducing the scientific theory that populations evolve over the course of generations through a process of natural selection, established biological evolution as the primary explanation for species diversification. The first edition was published in 1859. This book will remain a must-read for anyone interested in evolutionary biology, and the role of natural selection in diversification in particular.

• Givnish, Thomas J., and Kenneth J. Sytsma. 1997. Molecular evolution and adaptive radiation. Cambridge, UK: Cambridge Univ. Press.

  Contributors in this multi-authored book address questions related to adaptive radiation by combining complementary approaches in comparative molecular genetics, phylogenetics, ecology, and biogeography. The synthetic chapter by Givnish (pp. 1–54) is still very relevant and a good starting point for anyone interested in the study of adaptive radiation.

• Grant, Peter R., and B. Rosemary Grant. 2008. How and why species multiply: The radiation of Darwin’s finches. Princeton, NJ: Princeton Univ. Press.

  In this very accessible book, Peter and Rosemary Grant explain what we have learned about the origin and evolution of new species through the study of one of the most famous adaptive radiations, that of Darwin’s finches.

• Lack, David. 1983. Darwin’s finches. Cambridge, UK: Cambridge Univ. Press.

  Lack’s work on Darwin’s finches not only set the foundation for the study of this remarkable group of species, it also outlined some of the most relevant questions related to the study of adaptive radiation. This book has not lost its relevancy, and it remains among the most fascinating readings in evolutionary biology. Originally published in 1947, this edition includes an introduction and notes by Laurene M. Ratcliffe and Peter T. Boag.

• Losos, Jonathan B. 2009. Lizards in an evolutionary tree: Ecology and adaptive radiation of anoles. Berkeley: Univ. of California Press.

  Perhaps one of the best-studied examples of adaptive radiation involves Caribbean Anolis lizards. With about four hundred species, Anolis has played an important role in the development of ecological theory and has become a model system exemplifying the integration of ecological, evolutionary, and behavioral studies to understand evolutionary diversification. This major work reviews and synthesizes an immense literature.

• Schluter, Dolph. 2000. The ecology of adaptive radiation. Oxford: Oxford Univ. Press.

  This book investigates all aspects of the ecological theory of adaptive radiation, which stipulates that lineage diversification in adaptive radiation is the result of divergent natural selection. The book focuses mainly on diversification unfolding on relatively small temporal and spatial scales. It makes use of a wide range of examples to dissect and detail the main ecological processes in adaptive radiation,

• Simpson, George G. 1953. The major features of evolution. New York: Columbia Univ. Press.

  This book is an extensively revised version of Tempo and Mode in Evolution, originally published in 1944 by the same author. It complements nicely the original publication and will be as satisfying to the reader

• Simpson, George G. 1984. Tempo and mode in evolution. New York: Columbia Univ. Press.

  This book focuses on the rate and process of evolution and remains a classic contribution to the study of adaptive radiation and the process of evolution in general. The material is very accessible, focusing mostly on paleontological examples of diversification. Simpson has added an introduction to the 1984 edition of this book, originally published in 1944.