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Modeling the Size Spectrum for Macroinvertebrates and Fishes in Stream Ecosystems
Published on: July 30, 2019
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Prey size structure diminishes cascading effects by increasing interference competition and predation among prey
Ecology
|November 24, 2015
Summary
Organism size significantly impacts ecological interactions. Changes in intermediate prey size or abundance can affect food webs as much as top predator changes, suggesting food chains can withstand top predator loss.
Area of Science:
- Ecology
- Marine Biology
- Food Web Dynamics
Background:
- Organism size influences species interactions, including consumption, competition, and avoidance.
- Trophic cascades are complex interactions within food webs, influenced by predator and prey dynamics.
Purpose of the Study:
- To investigate how the size of top predators (toadfish) and intermediate prey (mud crabs) affect consumptive and behavioral interactions in a tri-trophic food chain.
- To understand the role of intraguild predation and interference competition in structuring marine food webs.
Main Methods:
- Two mesocosm experiments were conducted using a food chain: toadfish (top predator), mud crabs (intermediate prey), and oysters (basal resource).
- Experiment 1 systematically varied predator and prey sizes to assess consumption and oyster survival.
- Experiment 2 differentiated crab mortality sources (intraguild vs. interguild predation).
Main Results:
- Crab biomass consumed depended on crab size, not toadfish size, with no cascade effect on oyster survival.
- Oyster survival increased due to crab interference competition (without toadfish) and predator-avoidance behavior (with toadfish).
- Crab mortality was similar with or without toadfish when all sizes were present, indicating significant intraguild predation.
Conclusions:
- Changes in intermediate prey size/abundance can impact trophic interactions similarly to changes in top predator abundance.
- Simple food chains may be resilient to the loss of higher trophic levels.
- Intraguild predation and interference competition play crucial roles in food web dynamics.
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