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Evolution's Wedge

Competition and the Origins of Diversity

David Pfennig

Publication Year: 2012

Evolutionary biology has long sought to explain how new traits and new species arise. Darwin maintained that competition is key to understanding this biodiversity and held that selection acting to minimize competition causes competitors to become increasingly different, thereby promoting new traits and new species. Despite Darwin’s emphasis, competition’s role in diversification remains controversial and largely underappreciated.

In their synthetic and provocative book, evolutionary ecologists David and Karin Pfennig explore competition's role in generating and maintaining biodiversity. The authors discuss how selection can lessen resource competition or costly reproductive interactions by promoting trait evolution through a process known as character displacement. They further describe character displacement’s underlying genetic and developmental mechanisms. The authors then consider character displacement’s myriad downstream effects, ranging from shaping ecological communities to promoting new traits and new species and even fueling large-scale evolutionary trends. Drawing on numerous studies from natural populations, and written for a broad audience, Evolution’s Wedge seeks to inspire future research into character displacement’s many implications for ecology and evolution.

Published by: University of California Press

Series: Organisms and Environments


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pp. 1-1

Title Page, Series Page, Copyright

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pp. 2-5

Table of Contents

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pp. v-viii

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pp. ix-xiv

This book examines how a pervasive feature of living systems — competition — drives evolution and generates diversity. Competitive interactions take place whenever any two individuals, populations, or species affect each other adversely. These interactions might involve direct contests for limiting resources or reproductive opportunities. ...

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Chapter 1. Discovery of a Unifying Principle

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pp. 1-28

In a frequently heard — and perhaps apocryphal — story, the evolutionary biologist J. B. S . Haldane, when asked to comment on what could be inferred about the Creator based on the creation, is reported to have said, “He must have had an inordinate fondness of beetles” (Farrell 1998). ...

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Chapter 2. Why Character Displacement Occurs

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pp. 29-56

In chapter 1, we defined “character displacement” as trait evolution that arises as an adaptive response to resource competition or deleterious reproductive interactions between species. Left unaddressed in that chapter, however, were the causes of resource competition or deleterious reproductive interactions between species. ...

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Chapter 3. When Character Displacement Occurs

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pp. 57-80

In the previous two chapters, we examined how character displacement arises as an adaptive response to resource competition or deleterious reproductive interactions between species. A key unresolved issue, however, is why some populations and species are more likely to undergo character displacement as opposed to the alternative outcomes of competitive exclusion ...

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Chapter 4. How Character Displacement Unfolds

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pp. 81-104

Recall from chapter 3 that a key facilitator of character displacement is the presence of standing phenotypic variation on which competitively mediated selection can act. Yet, relatively little is known about the source(s) of such variation or how different sources affect character displacement’s tempo and mode. ...

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Chapter 5. Diversity and Novelty Within Species

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pp. 105-132

Most species exhibit a striking amount of phenotypic variation. Indeed, in some cases, trait variation between different members of the same species is as great as that normally seen between different species (see, for example, Figure 1.1B, C). Here we consider the role of competitively mediated selection in generating and maintaining such diversity within species. ...

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Chapter 6. Ecological Consequences

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pp. 133-156

Having focused on the causes of character displacement in the first half of the book, we now explicitly examine some of the consequences of character displacement, starting with its ecological consequences. In this chapter, we consider how the study of character displacement provides a unifying framework for understanding the maintenance, abundance, and distribution of biodiversity. ...

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Chapter 7. Sexual Selection

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pp. 157-178

In chapter 6, we examined the ecological ramifications of character displacement. For the remainder of the book, we discuss character displacement’s evolutionary implications, starting with its implications for sexual selection. ...

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Chapter 8. Speciation

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pp. 179-204

Understanding how species arise (“speciation”) is essential for explaining the origins of diversity. Until this point in the book, we have only briefly mentioned the possible contribution of character displacement to speciation. Here, we explicitly consider character displacement’s role in the formation of new species. ...

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Chapter 9. Macroevolution

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pp. 205-232

Macroevolution is large-scale evolutionary change, ranging from the origin of species and major new features (such as novel traits or even new body plans) to long-term evolutionary trends (Stanley 1979; Erwin 2000; Levinton 2001; Gould 2002; Futuyma 2009). Beginning with Darwin, many evolutionary scientists have held that macroevolution reflects the long-term accumulation ...

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Chapter 10. Major Themes and Unsolved Problems

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pp. 233-242

At the outset of this book, we emphasized that a longstanding problem in both evolutionary biology and ecology is to explain why there are so many different kinds of living things and why even closely related organisms tend to differ from one another phenotypically (for example, see Figure 1.1). ...


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pp. 243-290


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pp. 291-303

Production Notes

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pp. 319-319

E-ISBN-13: 9780520954045
Print-ISBN-13: 9780520274181

Page Count: 320
Publication Year: 2012

Series Title: Organisms and Environments
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OCLC Number: 834914469
MUSE Marc Record: Download for Evolution's Wedge

Research Areas


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Subject Headings

  • Divergence (Biology).
  • Competition (Biology).
  • Animal diversity.
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