Flow-network organization in ecosystems and the mathematical theory of information

Ecological flow networks are described by means of the Theory of Graphs and characterised by two quantities of the Mathematical Theory of Information, namely the Internal Information Transfer (a measure of the Specialization) and the Joint Entropy (a measure of Connectivity). Both indexes fall into a narrow interval of values. This tendency of real stable ecosystems is interpreted in the light of two variational adaptative principIes.