In the last decades, many works investigated the trophic structure of communities stressing, in particular, the role played by species in food webs (e.g., their trophic level and, more recently, their centrality). There exist some encouraging applications, but few details are known about the relationships between centrality measurements and trophic levels. In addition, these studies almost refer to unweighted trophic networks, despite the acknowledged need of investigating weighted webs. Here we aim to contribute to the synthetic treatment of these complementary issues by analyzing several indices of centrality and trophic level. Studying 19 ecosystems, we ranked the nodes according to their positional importance values (based on various centrality indices) and we compared the rank order of coefficients with unweighted or weighted trophic levels. Our goal was revealing potential biases in finding high centrality nodes among basal, intermediate and top species. We found that key species occupy intermediate positions of the trophic hierarchy. In case of unweighted data, trophic levels of key nodes do not deviate from trends displayed by the whole dataset. Significant differences were observed when using weighted data. These results contradict the common belief of many ecologists that identified top-predators and charismatic megafauna as main targets of conservation policies. We discuss the potential consequences of the observed features on ecosystem dynamics.
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FooD Webs: Integration of Patterns and Dynamics
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Albert, R., H. Jeong and A.-L. Barabási. 2000. Error and attack tolerance of complex networks.
Barabási A.-L., 'Error and attack tolerance of complex networks' (2000) 406Nature: 378-381.
Barabási A.-L.Error and attack tolerance of complex networksNature2000406378381)| false
Coll, M., L.J. Shannon, C.L. Moloney, I. Palomera and S. Tudela. 2006. Comparing trophic flows and fishing impacts of a NW Mediterranean ecosystem with coastal upwelling systems by means of standardized models and indicators.
Tudela S., 'Comparing trophic flows and fishing impacts of a NW Mediterranean ecosystem with coastal upwelling systems by means of standardized models and indicators' (2006) 198Ecol. Model.: 53-70.
Tudela S.Comparing trophic flows and fishing impacts of a NW Mediterranean ecosystem with coastal upwelling systems by means of standardized models and indicatorsEcol. Model.20061985370)| false
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Ulanowicz R.E.Network Analysis in Marine Ecology1989)| false