Topological Properties of Food Webs: From Real Data to Community Assembly Models

We explore patterns of trophic connections between species in the largest and highest-quality empirical food webs to date, introducing a new topological prop- erty called the degree distribution, defined as the frequency of species SL with L links. Non-trivial differences are shown in degree distributions between species-rich and species-poor communities, which might have important consequences for ecosys- tems' responses to disturbances. Species richness-connectance (SC) and number of links-species richness (LS) relationships observed provide no support for the theory of LS scaling law or constant connectance for food webs. We further explore these observations by means of simulated food webs resulting from random multitrophic assembly models. SC and LS relationships of real food webs are reproduced, but degree distributions are not properly predicted. The best agreement between em- pirical and simulated webs occurs when weak interaction strengths between species govern food web dynamics.