Ecological networks, nestedness and sampling effort

1. Ecological networks have been shown to display a nested structure. To be nested, a network must consist of a core group of generalists all interacting with each other, and with extreme specialists interacting only with generalist species. 2. Studies on ecological networks are especially prone to sampling effects, as they involve entire species assemblages. However, we know of no study addressing to what extent nestedness depends on sampling effort, despite the numerous studies discussing the ecological and evolutionary implications of nested networks. 3. Here we manipulate sampling effort in time and space and show that nestedness is less sensitive to sampling effort than number of species and links within the network. 4. That a structural property of an ecological network appears less prone to sampling bias is encouraging for other studies of ecological networks. This is because it indicates that the sensitivity of ecological networks properties to effects of sampling effort might be smaller than previously expected.