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Marine Ecology Progress Series

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MEPS 273:291-302 (2004)  -  doi:10.3354/meps273291

Network structure and robustness of marine food webs

Jennifer A. Dunne1,4,*, Richard J. Williams2,4, Neo D. Martinez3,4

1Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501, USA
2National Center for Ecological Analysis and Synthesis, University of California Santa Barbara, 735 State St., Suite 300, Santa Barbara, California 93101-3351, USA
3Center for Applied Mathematics, 657 Frank HT Rhodes Hall, Cornell University, Ithaca, New York 14853, USA
4Pacific Ecoinformatics and Computational Ecology Lab, Rocky Mountain Biological Laboratory, PO Box 519, Crested Butte, Colorado 81224, USA

ABSTRACT: Previous studies suggest that food-web theory has yet to account for major differences in food-web properties of marine versus other types of ecosystems. We examined this issue by analyzing the network structure of food webs for the Northeast US Shelf, a Caribbean reef, and Benguela, off South Africa. The values of connectance (links per species2), link density (links per species), mean chain length, and fractions of intermediate, omnivorous, and cannibalistic taxa of these marine webs are somewhat high but still within the ranges observed in other webs. We further compared the marine webs by using the empirically corroborated niche model that accounts for observed variation in diversity (taxon number) and complexity (connectance). Our results substantiate previously reported results for estuarine, fresh-water, and terrestrial datasets, which suggests that food webs from different types of ecosystems with variable diversity and complexity share fundamental structural and ordering characteristics. Analyses of potential secondary extinctions resulting from species loss show that the structural robustness of marine food webs is also consistent with trends from other food webs. As expected, given their relatively high connectance, marine food webs appear fairly robust to loss of most-connected taxa as well as random taxa. Still, the short average path length between marine taxa (1.6 links) suggests that effects from perturbations, such as overfishing, can be transmitted more widely throughout marine ecosystems than previously appreciated.

KEY WORDS: Food webs · Network structure · Marine ecosystems · Robustness · Connectance · Niche model · Biodiversity loss

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