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5 - Responses to Environmental Change: Adaptation or Extinction
- Edited by Régis Ferrière, Ecole Normale Supérieure, Paris, Ulf Dieckmann, International Institute for Applied Systems Analysis, Austria, Denis Couvet, Muséum National d'Histoire Naturelle, Paris
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- Book:
- Evolutionary Conservation Biology
- Published online:
- 15 August 2009
- Print publication:
- 10 June 2004, pp 85-100
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Summary
Introduction
All populations are confronted with a plethora of environmental changes and must adapt, shift their range, or face extinction. Adaptation may take two forms:
The first option involves physiological acclimatization through phenotypic plasticity at the level of individuals.
Second, the genetic composition of populations may change through natural selection, a change that favors some genotypes at the expense of others.
Whereas plastic adaptation can only cope with environmental change of a limited extent, genetic adaptation allows populations to persist outside their previous tolerance ranges. Therefore, genetic adaptation is of primary concern in conservation biology, in terms of what is required to cope with major or sustained environmental changes. Feasibility and speed of genetic adaptations in response to environmental change depend on a variety of factors, such as a population's genetic diversity, the population size, generation time, and reproduction excess.
This chapter is organized as follows. In Section 5.2 we review the different types of abiotic environmental change that occur in nature, with an emphasis on their characteristic spatial and temporal scales. Section 5.3 explains how changes in local climate affect the physiological and phenological aspects of life histories and shows that evolutionary adaptations to altered climate conditions can be rapid. Sections 5.4 and 5.5 extend this conclusion to responses to thermal stress and pollution, and Section 5.6 highlights the special evolutionary challenges experienced by endangered species.
7 - Is Optimality Over the Hill? The Fitness Landscapes of Idealized Organisms
- Edited by Steven Hecht Orzack, The Fresh Pond Research Institute, Cambridge, MA, Elliott Sober, University of Wisconsin, Madison
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- Book:
- Adaptationism and Optimality
- Published online:
- 06 January 2010
- Print publication:
- 04 June 2001, pp 219-241
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Summary
Imagine a mountaineering enthusiast who decides to write a comprehensive guide for climbers. This would-be author spends many years climbing every peak throughout the world, gathering material for a book, and then starts to write. In the end, our enthusiast produces a guidebook, listing each peak, its longitude and latitude, and the number of climbers the author encountered at the summit.
Clearly, this guidebook is unlikely to make the best-seller list or even to become a citation classic. Readers of this guide would undoubtedly have many additional questions: What is the height of each peak? How steep is the approach to the summit from different directions? Are there ridges leading to the peak? Are there other peaks nearby? When asked about these questions, the author replies in defense, “Climbers climb peaks, so I wrote about peaks.”
In our view, many (perhaps most) studies of optimality in biology seem similar to this guidebook. The primary questions of interest are “Where is the fitness peak?” and “Is the population or species of interest currently at or near the peak?” The rationale for this emphasis is that, because evolution by natural selection is expected (under certain conditions) to increase the mean fitness of a population, one might predict that populations would tend to reside at the peaks in a fitness landscape.
Although fitness peaks are interesting, we fear that an exclusive emphasis on them may generate an understanding of phenotypic selection and evolution that is as unsatisfying as our imaginary mountaineering guidebook. We suggest that a broader view that explores the topography of fitness landscapes may be useful.