A Necessary and Sufficient Assembly Rule for Real Ecosystems

I will demonstrate how a simple empirical regularity observed in the topology of real food webs may be used to mathematically deduce a necessary and sufficient constraint operating during system assembly. This differs from the classical bottom-up approach for studying ecosystem structure in that “plausible” assembly rules are not used to induce large scale patterns, but rather, a macroscopic regularity is used to deduce an assembly rule. This is an extension of results reported earlier on patterns in the graphical structure of food webs (Sugihara 1983, 1984).