Competition and Coexistence

The question "Why are there so many species?" has puzzled ecologist for a long time. Initially, an academic question, it has gained practical interest by the recent awareness of global biodiversity loss. Species diversity in local ecosystems has always been discussed in relation to the problem of competi­ tive exclusion and the apparent contradiction between the competitive exclu­ sion principle and the overwhelming richness of species found in nature. Competition as a mechanism structuring ecological communities has never been uncontroversial. Not only its importance but even its existence have been debated. On the one extreme, some ecologists have taken competi­ tion for granted and have used it as an explanation by default if the distribu­ tion of a species was more restricted than could be explained by physiology and dispersal history. For decades, competition has been a core mechanism behind popular concepts like ecological niche, succession, limiting similarity, and character displacement, among others. For some, competition has almost become synonymous with the Darwinian "struggle for existence", although simple plausibility should tell us that organisms have to struggle against much more than competitors, e.g. predators, parasites, pathogens, and envi­ ronmental harshness.

1 Introduction.- 1.1 The Intellectual Debate Until 1990.- 1.2 Progress During the Last Decade.- 1.3 Consequences for the Structure of the Book.- References.- 2 Competition in Well-Mixed Habitats: From Competitive Exclusion to Competitive Chaos.- 2.1 Introduction.- 2.2 Competition for a Single Abiotic Resource.- 2.3 Resource Storage.- 2.4 Competition for a Single Biotic Resource.- 2.5 Competition for Two Resources.- 2.6 Competition for Three Resources.- 2.7 Discussion.- References.- 3 Spatial Models of Competition.- 3.1 Introduction.- 3.2 Implicitly Spatial Models.- 3.3 Explicitly Spatial Models.- 3.4 Comparing and Connecting Methods.- 3.5 Underlying Spatial Heterogeneity.- 3.6 Competition and Coexistence.- 3.7 Future Directions.- References.- 4 Competition and Coexistence in Plankton Communities.- 4.1 Introduction.- 4.2 Competition Experiments in Laboratory Microcosms.- 4.3 Experiments in Field Mesocosms.- 4.4 Tests of the Intermediate Disturbance Hypothesis by Field Data.- 4.5 Herbivory and Diversity.- 4.6 The Role of Abundance and of Seasonality.- 4.7 Conclusions.- References.- 5 Competition and Coexistence in Mobile Animals.- 5.1 Introduction.- 5.2 Competition Among Mobile Animals.- 5.3 Heterogeneity, Trade-Offs, and Competition.- 5.4 Scale and Heterogeneity.- 5.5 New Challenges.- References.- 6 Competition, Coexistence and Diversity on Rocky Shores.- 6.1 Introduction.- 6.2 Disruption of Competitive Exclusion: The Non-Equilibrium View.- 6.3 Coexistence Through Trade-Offs: The Equilibrium View.- 6.4 Synthesis: Integrating the Effects of Competition, Consumption and Disturbance.- 6.5 Conclusion.- References.- 7 Competition and Coexistence in Terrestrial Plants.- 7.1 Introduction.- 7.2 Competition.- 7.3 Coexistence.- 7.4 Conclusion.- References.- 8 Synthesis: Back to Santa Rosalia, or No Wonder There Are So Many Species.- 8.1 Trade-Offs.- 8.2 Disturbance, Predation and Competition.- 8.3 The Spatial Dimension.- 8.4 Self-Generated Heterogeneity.- 8.5 Exclusive Resources.- 8.6 Slow Exclusion.- 8.7 Equilibrium vs. Non-Equilibrium Concepts.- 8.8 Future Challenges.- References.