Adaptive Radiation

by

Linyi Zhang, Scott P. Egan

• LAST REVIEWED: 28 April 2023
• LAST MODIFIED: 27 March 2019
• DOI: 10.1093/obo/9780199830060-0214

Introduction

The spectacular diversity of life on earth presents one of the most intriguing questions for biologists: why and how does the variation among organisms arise? One powerful concept that has its origins with Darwin (late 1800s) and was developed in detail during the Modern Synthesis (early to mid-1900s), is “adaptive radiation.” This evolutionary process refers to the rapid diversification of a single lineage into many different species during which different morphological/ecological traits evolve in association with different environments and niches. The central components of adaptive radiation are (1) rapid diversification of multiple species from a single common ancestor and (2) different species exhibit different ecological traits that are adaptive to different niches. While many great individual cases of adaptive radiation have been studied, such as Darwin’s finches, African rift lake cichlids, and Hawaiian silverswords, controversies remain on topics such as the definition of an adaptive radiation, the appropriate approach to test for it, and the ultimate causes of an adaptive radiation. This article provides a general overview of the literature addressing the study of adaptive radiation, including taxa-specific examples and major literature reviews. The article will highlight literature that helps to clarify the concept of adaptive radiation by distinguishing it from other related biological processes. Then the literature on specific approaches to test for adaptive radiation is featured. Next, connections to the literature aiming to understand the proximate and ultimate causes of adaptive radiation are provided, including explicit tests of the role of ecology, as well as an exploration of the source of genetic variation and geographic conditions promoting adaptive radiation. Lastly, we connect to the literature addressing the constraints on adaptive radiations. Overall, this article will address research on the origin of new species and the evolution of ecological differences between them.

General Overview

The conceptual framework of adaptive radiations and its importance in generating biodiversity were laid out in Lack 1947 and Simpson 1953. Lack 1947 and Simpson 1953 developed the idea of how ecology (ecological opportunities and interspecific competition) promotes rapid proliferation and diversification of organisms into different environments. For a more modern update on adaptive radiations, see the pivotal book Schluter 2000 and a review chapter Losos and Mahler 2010. Schluter 2000 both summarizes and synthesizes the current state of the field, including many new comparative analyses across systems. Givnish and Sytsma 1997 put together studies of adaptive radiation across a diverse set of taxonomic groups and thus serves as a great guide to the most prominent examples of adaptive radiation (plants: Hawaiian silverswords and lobeliads; mammals: Australian marsupials; birds: Darwin’s finches; amphibians: Anolis lizards; insects: Hawaiian Drosophila; fish: Cichlid fish and sticklebacks). An example of adaptive radiation in microbes (i.e., coral reef endosymbionts) is documented by Thornhill, et al. 2014. Lastly, two of the most well-known examples of adaptive radiations are summarized in Grant and Grant 2008 (Darwin’s finches) and Losos 2009 (Anolis lizards), where the authors have spent their careers investigating these issues in a single system.

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

  This edited volume assembles studies of adaptive radiation across a wide set of taxonomic groups.

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

  This book reviews the molecular and ecological evidence documenting the adaptive radiation of Darwin’s finches from the author’s thirty-plus years of field studies on this system.

• Lack, D. 1947. Darwin’s Finches. Cambridge, UK: Cambridge Univ. Press.

  A classic work on Darwin’s Finches that incorporates ecology (inter-species competition) as an important driver in adaptive radiation.

• Losos, J. 2009. Lizards in an evolutionary tree. Oakland: Univ. of California Press.

  DOI: 10.1525/california/9780520255913.001.0001

  Similar to Grant and Grant 2008, this book comprehensively synthesized the literature on the study of Caribbean Anolis lizards, which are a classic example of adaptive radiation.

• Losos, J. B., and D. L. Mahler. 2010. Adaptive radiation: The interaction of ecological opportunity, adaptation, and speciation. In Evolution after Darwin: The first 150 years. Edited by M. A. Bell, D. J. Futuyma, W. F. Eanes, and J. S. Levinton, 381–420. Sunderland, MA: Sinauer Press.

  This book chapter reviews studies of adaptive radiation.

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

  Focuses on summarizing the ecology theory as the cause of the adaptive radiation and synthesizing the data available at the time of publication. This is an influential book on this topic.

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

  Proposes a central role of adaptive radiation in generating biodiversity from a paleontological perspective. Specifically, chapters 6 and 7 discuss the importance of ecological adaptation in speciation.

• Thornhill, D. J., A. M. Lewis, D. C. Wham, and T. C. LaJeunesse. 2014. Host-specialist lineages dominate the adaptive radiation of reef coral endosymbionts. Evolution 68:352–367.

  DOI: 10.1111/evo.12270

  Presents a rare example of adaptive radiation in eukaryotic microbes—the microbial endosymbionts of reef corals.