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Two degrees of separation in complex food webs
Richard J Williams1, Eric L Berlow, Jennifer A Dunne
1Romberg Tiburon Center and Department of Biology, San Francisco State University, 3150 Paradise Drive, Tiburon, CA 94920, USA.
Summary
Species in ecosystems are more connected than previously believed, with most within three links of each other. This highlights how biodiversity loss and species invasions impact more species in food webs.
Area of Science:
- Ecology
- Ecosystem Dynamics
- Food Web Analysis
Background:
- Feeding relationships significantly impact species populations and community structures.
- Strong ecological effects are typically limited to three links within food webs.
- The extent of species interactions in complex food webs remains largely unquantified.
Purpose of the Study:
- To quantify the interconnectedness of species within complex food webs.
- To determine the average and maximum reach of ecological influence in ecosystems.
- To investigate the relationship between network complexity, species richness, and species proximity.
Main Methods:
- Analysis of seven large, complex empirical food webs from diverse ecosystems.
- Utilization of a food-web model to generalize findings beyond empirical data.
- Calculation of the number of links separating species within these networks.
Main Results:
- Species in large ecosystems are, on average, two links apart.
- >95% of species are found within three links of each other.
- Species proximity increases with network complexity and species richness.
Conclusions:
- Ecosystems exhibit a higher degree of species interconnectedness than previously assumed.
- Biodiversity loss and invasive species may have broader impacts than currently understood.
- Findings underscore the importance of species interactions in ecosystem stability and function.