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ÁLLATTANI KÖZLEMÉNYEK (2007) 92(2): 71–78. Structure and function in an ecosystem – a food web study (Prince William Sound, Alaska) BARBARA BAUER 1 and FERENC JORDÁN 2 Szent István University, Faculty of Veterinary Science, Institute of Zoology, Rottenbiller u. 50., 1077, Budapest, Hungary E–mail: [email protected] 2 Hungarian Natural History Museum, Animal Ecology Research Group of HAS, Ludovika tér 2., 1083, Budapest, Hungary 1 Abstract. Several possible views exist on how could we find those species that play important roles in ecosystems. One such method is to define species in central positions in the interaction network. There are several network indices for quantifying centrality but it is difficult to test the predictions of these network analytical techniques. Techniques for assessing functional importance are also emerging, and these are exemplified in mass-balance modelling applications. In this paper, we calculate 13 structural and 4 functional importance indices for the trophic components of the ecosystem model of Prince William Sound, Alaska and examine their relationships. We evaluate the correlation between these indices with the Spearman rank correlation coefficient. Our results show the importance of weighting links in a network and paying attention not only to the local, but also to the indirect interactions of a node. We have found that a structural index gives surprisingly similar results to those of the much more complicated dynamic simulation models. Our paper may contribute to the better understanding of the relationship between stucture and dynamics, because it is one of the first approaches to test the reality of conclusions drawn from examining a network. Keywords: keystone species, ecosystem, food web, centrality.
