Food Web Topology and Nested Keystone Species Complexes

Figure 1

Toy network illustrating the nonnested centrality of node sets. The number of nodes reachable from nodes , , , and in two steps () equals 11, 9, 9, and 7, respectively. Thus, node has the highest -reach centrality in the network. Yet, from the () set of nodes only 12 and from the () or () set of nodes only 13, while from the () set of nodes, 14 other nodes are reachable in two steps. Thus, the () set is more central than the other sets, based on reachability. The highest centrality node () is not a subset of the highest centrality set of two nodes ().