Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgements
- List of abbreviations
- 1 Introduction
- 2 Studying change
- 3 Key concepts in plant evolution
- 4 The origin and extent of human-influenced ecosystems
- 5 Consequences of human influences on the biosphere
- 6 Categories
- 7 Investigating microevolution in plants in anthropogenic ecosystems
- 8 Plant microevolution in managed grassland ecosystems
- 9 Harvesting crops: arable and forestry
- 10 Pollution and microevolutionary change
- 11 Introduced plants
- 12 Endangered species: investigating the extinction process at the population level
- 13 Hybridisation and speciation in anthropogenically influenced ecosystems
- 14 Ex situ conservation
- 15 In situ conservation: within and outside reserves
- 16 Creative conservation through restoration and reintroduction
- 17 Reserves in the landscape
- 18 Climate change
- 19 Microevolution and climate change
- 20 The implications of climate change for the theory and practice of conservation
- 21 Overview
- References
- Index
12 - Endangered species: investigating the extinction process at the population level
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Acknowledgements
- List of abbreviations
- 1 Introduction
- 2 Studying change
- 3 Key concepts in plant evolution
- 4 The origin and extent of human-influenced ecosystems
- 5 Consequences of human influences on the biosphere
- 6 Categories
- 7 Investigating microevolution in plants in anthropogenic ecosystems
- 8 Plant microevolution in managed grassland ecosystems
- 9 Harvesting crops: arable and forestry
- 10 Pollution and microevolutionary change
- 11 Introduced plants
- 12 Endangered species: investigating the extinction process at the population level
- 13 Hybridisation and speciation in anthropogenically influenced ecosystems
- 14 Ex situ conservation
- 15 In situ conservation: within and outside reserves
- 16 Creative conservation through restoration and reintroduction
- 17 Reserves in the landscape
- 18 Climate change
- 19 Microevolution and climate change
- 20 The implications of climate change for the theory and practice of conservation
- 21 Overview
- References
- Index
Summary
The evidence presented in previous chapters makes it plain that human activities create profound and highly complex changes in ecosystems through the imposition of new selection pressures. Darwin predicted that selection favours those species and populations that have the necessary genetic variability to survive and prosper under changing conditions. In contrast, species and populations that lack the necessary Darwinian fitness for the new conditions are at a selective disadvantage, and are in danger of becoming extinct.
This chapter analyses the extinction processes at the population level, providing the necessary background to a key issue to be examined below. Can the extinction of species/populations be prevented by appropriate conservation management?
As a prelude to the discussion on extinction, it is important, as always, to understand Darwin's own view of the vulnerability of rare species and appreciate his insight that extinction is often the end point of a process of decline. In the Origin (Darwin, 1901, 79–80), he writes:
Natural selection acts solely through the preservation of variations in some way advantageous, which consequently endure. Owing to the high geometric rate of increase of all organic beings, each area is already fully stocked with inhabitants; and it follows from this, that as the favoured forms increase in number, so, generally, will the less favoured decrease and become rare. Rarity, as geology tells us, is the precursor to extinction. We can see that any form which is represented by few individuals will run a good chance of utter extinction, during great fluctuations in the nature of the seasons, or from a temporary increase in the number of its enemies. […]
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- Publisher: Cambridge University PressPrint publication year: 2009