"Network dimension and the topology of life"
Consider a directed network model, interpreted as an ecosystems (nodes are species and links are interactions). A new metric is defined - local network dimension, LND - that decreases with the degree of specialization of a species. LND defines the "ecological niche" in a network system: When LND grows above 2, the species undergoes evolutionary branching, under 1 the species undergoes extinction. Dynamics of ecological interactions are defined by changes in size of the LND of "meta-nodes" aggregating several species and the sign of the interactions between them.