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Testing the mechanisms by which source-sink dynamics alter competitive outcomes in a model system.
1Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada.
The American Naturalist
|September 20, 2007
Summary
Dispersal impacts species competition by altering population dynamics, not just by moving individuals between habitats. This study shows dispersal modifies demographic rates, influencing competitive outcomes in ecological systems.
Area of Science:
- Ecology
- Population Dynamics
- Community Ecology
Background:
- Dispersal between habitats influences local competitive interactions through source-sink dynamics.
- Source-sink dynamics are traditionally understood to affect competition via spatial subsidies, redistributing individuals.
- An alternative mechanism, demography modification, suggests dispersal alters species' per capita demographic rates.
Purpose of the Study:
- To investigate whether spatial subsidies alone explain the impact of source-sink dynamics on competitive outcomes.
- To test the role of demography modification in altering competitive outcomes due to dispersal.
Main Methods:
- Utilized protist microcosms (bacterivorous ciliates) to model exploitative competition.
- Established high-enrichment (source) and low-enrichment (sink) environments.
- Compared long-term competitive outcomes with and without dispersal, using mathematical models to analyze population dynamics.
Main Results:
- Dispersal significantly altered competitive outcomes among protist species.
- Mathematical modeling indicated that spatial subsidies were insufficient to explain the observed effects of dispersal.
- Alternative models strongly supported demography modification as a key factor influencing competitive outcomes.
Conclusions:
- Dispersal's influence on competitive outcomes extends beyond simple redistribution of individuals.
- Demography modification, where dispersal alters per capita demographic rates, is a significant determinant of competition.
- Provides the first empirical evidence for the role of demography modification in dispersal-mediated competition.
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