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Journal of Theoretical Biology 230 (2004) 351358 Who dominates whom in the ecosystem? Energy flow bottlenecks

Summary: Journal of Theoretical Biology 230 (2004) 351358
Who dominates whom in the ecosystem? Energy flow bottlenecks
and cascading extinctions$
Stefano Allesina*, Antonio Bodini
Department of Environmental Sciences, University of Parma, Viale delle Scienze, 11/A, Parma 43100, Italy
Received 25 February 2004; received in revised form 20 May 2004; accepted 25 May 2004
Available online 17 July 2004
In this paper, we investigate the problem of secondary extinction in food webs through the use of dominator trees, network
topological structures that reduce food webs to linear pathways that are essential for energy delivery. Each species along these chains
is responsible for passing energy to the taxa that follow it, and, as such, it is indispensable for their survival; because of this it is said
to dominate them. The higher the number of species a node dominates, the greater the impact resulting from its removal. By
computing dominator trees for 13 well-studied food webs we obtained for each of them the number of nodes dominated by a single
species and the number of nodes that dominate each species. We illustrate the procedure for the Grassland Ecosystem showing the
potential of this method for identifying species that play a major role in energy delivery and are likely to cause the greatest damage if
removed. Finally, by means of two indices that measure error and attack sensitivity, we confirm a previous hypothesis that food
webs are very robust to random loss of species but very fragile to the selective loss of the hubs.
r 2004 Elsevier Ltd. All rights reserved.
Keywords: Food web; Energy flow; Bottleneck; Graph theory; Dominator; Secondary extinction; Species removal
1. Introduction


Source: Allesina, Stefano - Department of Ecology and Evolution, University of Chicago


Collections: Environmental Sciences and Ecology; Biology and Medicine