title: Network topology: patterns and mechanisms in plant-herbivore and host-parasitoid food webs.
abstract: 1. Biological communities are organized in complex interaction networks such as food webs, which topology appears to be non-random. Gradients, compartments, nested subsets and even combinations of these structures have been shown in bipartite networks. However, in most studies only one pattern is tested against randomness and mechanistic hypotheses are generally lacking. 2. Here we examined the topology of regional, coexisting plant-herbivore and host-parasitoid food webs to discriminate between the mentioned network patterns. We also evaluated the role of species body size, local abundance, regional frequency and phylogeny as determinants of network topology. 3. We found both food webs to be compartmented, with interaction range boundaries imposed by host phylogeny. Species degree within compartments was mostly related to their regional frequency and local abundance. Only one compartment showed an internal nested structure in the distribution of interactions between species, but species position within this compartment was unrelated to species size or abundance. 4. These results suggest that compartmentalization may be more common than previously considered, and that network structure is a result of multiple, hierarchical, non-exclusive processes.
authors.affiliation: Imbiv-Centro de Investigaciones Entomológicas de Córdoba. F.C.E.F. y N., Universidad Nacional de Córdoba Av. Vélez Sarsfield 1611 (X5016GCA), Córdoba, Argentina. lcagnolo@efn.uncor.edu
authors.forename: Luciano
authors.initials: L
authors.lastname: Cagnolo
authors.forename: Adriana
authors.initials: A
authors.lastname: Salvo
authors.forename: Graciela
authors.initials: G
authors.lastname: Valladares
mesh_terms: D000465:Algorithms; D000818:Animals; D001118:Argentina; D058448:Biota; D049628:Body Size; D020387:Food Chain; D006790:Host-Parasite Interactions; D007313:Insecta / Q000145:classification / Q000469:parasitology* / Q000502:physiology*; D010802:Phylogeny; D063245:Plant Development; D011156:Population Density; D013045:Species Specificity