Topological properties of food webs: from real data to community assembly models

Authors

  • Jose M. Montoya,

  • Ricard V. Solé


J. M. Montoya and R. V. Solé, ICREA-Complex Systems Lab, UPF Dr Aiguader 80, ES-08003 Barcelona, Spain.
JMM also at: Dept of Ecology, Univ. of Alcalá, ES-28871 Alcala de Henares, Madrid, Spain (jose.montoya@cexs.upf.es).
RVS also at: Santa Fe Institute, 1399 Hyde Park Road, NM 87501, USA.

Abstract

We explore patterns of trophic connections between species in the largest and highest-quality empirical food webs to date, introducing a new topological property called the link distribution frequency (i.e. degree distribution), defined as the frequency of species SL with L links. Non-trivial differences are shown in link distribution frequencies between species-rich and species-poor communities, which might have important consequences for the responses of ecosystems to disturbances. Coarse-grained topological properties observed, as species richness-connectance and number of links-species richness relationships, provide no support for the theory of links-species scaling law or constant connectance across empirical food webs investigated. We further explore these observations by means of simulated food webs resulting from multitrophic assembly models using different functional responses between species. Species richness-connectance and links-species richness relationships of empirical food webs are reproduced by our models, but degree distributions are not properly predicted, suggesting the need of new theoretical approximations to food web assembly. The best agreement between empirical and simulated webs occurs for low values of interaction strength between species, corroborating previous empirical and theoretical findings where weak interactions govern food web dynamics.

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