Evol Ecol Res 6: 1145-1166 (2004)     Full PDF if your library subscribes.

Reliability characteristics of natural functional group interaction webs

Andrew J. Davis,1* Wei-chung Liu,2 Joerg Perner1 and Winfried Voigt1

1Institute of Ecology, Friedrich Schiller University, Dornburger Strasse 159, 07743 Jena, Germany and  2Centre for Tropical Veterinary Medicine, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK

Address all correspondence to Andrew Davis, Institute of Low Temperature Science, Hokkaido University, Sapporo 060 0819, Japan.
e-mail: andrew@pop.lowtem.hokudai.ac.jp


We compare the reliability of interaction webs for functional groups derived from extensive field data. Reliability is the probability of a web continuing to function despite the failure of one or more functional groups. Interaction webs are diagrams of all the trophic and non-trophic relationships between groups. Functional groups are suites of species with similar roles in an ecosystem and, importantly, mediate the relationship between biodiversity and the functioning of ecosystems. How they interact will thus have major ecological consequences. We reveal interactions between groups by simple and partial Mantel tests and determine link type by applying sets of logical rules to the Mantel test results. We then calculate the reliability of the resulting interaction webs. We also derive the reliabilities for webs of different link types because web topology affects reliability, not just the number of groups and links. Using the qualities of sink webs derived from these interaction webs, we illustrate the overall patterns in the relationships between reliability and other web characteristics. We compare these with the relationships in food-webs. We demonstrate the relation of reliability to principal components representing the information common to web characteristics other than reliability. We show that reliabilities for webs of interactions between functional groups are very high, at least as high as those for food-webs, and that they show similar relationships to other web characteristics. Nevertheless, in our natural setting, it is the number of groups and the number of links a web has that most affects reliabilities. However, they also differ more between webs of different link types, where topology differs, than between sites. Thus, in nature, the reliability of webs of interactions between functional groups will depend on both web size and topology. This means that their contribution to mediating the relationship between biodiversity and ecosystem function will also depend on both web and topology.

Keywords: arthropods, biodiversity, ecosystem function, grasslands, plants, structure, topology.

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