A Statistical Test of Network Analysis: Can it Detect Differences in Food Web Properties? |
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Authors: | James K Dame Robert R Christian |
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Institution: | (1) Department of Biology, East Carolina University, Greenville, North Carolina 27858, USA;(2) Department of Environmental Studies, Sweet Briar College, Sweet Briar, VA 24595, USA |
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Abstract: | Ecological network analysis (ENA) is a modeling approach increasingly being used to examine food webs. However, most studies
do not replicate networks, and a statistical evaluation of ENA is lacking. The major objectives of this study, therefore,
were to evaluate statistically the effectiveness of ENA in detecting differences in food web properties and to compare ENA
output with established community level indices. Quantitative trophic networks (n = 12) representing four high salt marsh ponds during three times (corresponding to low stress, high stress, and post-disturbance)
were constructed from an extensive field sampling program augmented by literature values. Food webs of salt marsh ponds were
used because these systems contain relatively simple food webs, have well defined boundaries, and allow for adequate replication.
A null hypothesis was tested to determine how values of 12 indices from ENA output differed among the three stress/disturbance
conditions (H
o: low stress = high stress = post-disturbance). Results of both ANOVA and Friedman’s tests indicated most ENA indices were
significantly different among the three stress/disturbance conditions. The amount of covariance among the indices was relatively
low (7 of 66 were significant). Results were compared to differences in community indices (richness, evenness, and diversity)
among the three stress/disturbance conditions. ENA output identified differences beyond those recognized by the community
indices. Overall, networks were unique enough under different environmental conditions to provide statistically significant
differences in ENA results. Our findings are supportive of the use of carefully constructed networks in food web analysis
and for decision making in ecosystem-based management.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | ecological network analysis ecopath ecosystem-based management food web salt marsh pond stress trophic network |
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