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Detection of direct versus indirect effects: were experiments long enough?
1Department of Zoology, Oregon State University, Corvallis, Oregon 97331-2914, USA.
The American Naturalist
|May 1, 1997
Summary
Indirect effects in marine community studies appear quickly, not long after direct effects. Most experiments are long enough to capture these ecological interactions, suggesting community dynamics are predictable.
Area of Science:
- Ecology
- Marine Biology
- Community Ecology
Background:
- Ecological theory posits indirect effects in community regulation take longer to manifest than direct effects.
- This can lead to indirect effects being missed in manipulative studies.
- Understanding the temporal dynamics of direct and indirect effects is crucial for accurate ecological modeling.
Purpose of the Study:
- To evaluate if indirect effects in manipulative studies of community regulation become evident later than direct effects.
- To assess the impact of experiment duration on the observation of direct and indirect ecological effects.
- To determine if current experiment durations are sufficient to capture indirect effects in marine intertidal interaction webs.
Main Methods:
- Survey of marine intertidal interaction webs.
- Analysis of the effect of experiment duration on the emergence of direct and indirect effects.
- Statistical analysis of when effects became significant within the total experiment duration.
Main Results:
- Contrary to hypothesis, indirect effects appeared simultaneously or shortly after direct effects.
- Most direct and indirect effects became statistically significant within 20%-40% of the total experiment duration.
- A period of "constancy" was observed after the last indirect effect, indicating sufficient experiment duration.
Conclusions:
- Indirect effects in marine intertidal communities manifest much sooner than previously hypothesized.
- Current experimental durations are generally sufficient to observe the majority of indirect effects.
- Despite incomplete knowledge of indirect effects, community dynamics may be more predictable than ecological theory suggests.
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