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Predator identity and additive effects in a treehole community
Marcus W Griswold1, L Philip Lounibos
1University of Florida, Entomology and Nematology Department, P.O. Box 110620, Gainesville, Florida 32611, USA. marcgris@ufl.edu
Ecology
|May 9, 2006
Summary
Predator interactions in aquatic ecosystems can be complex. A study found that the combined effects of a top predator (Toxorhynchites rutilus) and an intermediate predator (Corethrella appendiculata) on mosquito larvae were predictable.
Area of Science:
- Ecology
- Aquatic Ecology
- Predator-Prey Dynamics
Background:
- Multiple predator species can create complex, nonadditive effects on lower trophic levels.
- Previous studies in aquatic systems suggest predator interactions are not always predictable from single-species effects.
Purpose of the Study:
- To investigate the individual and combined effects of a top and intermediate predator on native and invasive mosquito larvae.
- To test if a multiplicative risk model could predict the combined effects of these predators.
Main Methods:
- Used artificial treeholes as experimental aquatic systems.
- Examined the effects of Toxorhynchites rutilus (top predator) and Corethrella appendiculata (intermediate predator) individually and in combination.
- Monitored survivorship of native (Ochlerotatus triseriatus) and invasive (Aedes albopictus) mosquito larvae.
Main Results:
- The combined effects of both predators were accurately predicted by a multiplicative risk model, indicating additive effects.
- T. rutilus significantly decreased survivorship of both mosquito species.
- C. appendiculata increased native prey survivorship but decreased invasive prey survivorship.
- Intraguild predation occurred only after alternative prey was reduced by half.
- T. rutilus consumption increased over time, while C. appendiculata consumption decreased.
- C. appendiculata preferentially consumed A. albopictus, altering species composition.
- T. rutilus reduced overall prey density.
- Predator interference led to risk reduction when C. appendiculata density increased or predators were similarly sized.
Conclusions:
- Predator interactions in this system were largely additive and predictable by a multiplicative risk model.
- The intermediate predator influenced species composition, while the top predator reduced overall prey density.
- Predator interference can modify interaction outcomes, particularly at higher densities or when predators are similar in size.
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