  We investigate global stability and dynamics of large ecological networks by
classical methods of the dynamical system theory, including Hamiltonian
methods, and averaging. Our analysis exploits the network topological
structure, namely, existence of strongly connected nodes (hubs) in the
networks. We reveal new relations between topology, interaction structure and
network dynamics. We describe mechanisms of catastrophic phenomena leading to
sharp changes of dynamics and investigate how these phenomena depend on
ecological interaction structure. We show that a Hamiltonian structure of
interaction leads to stability and large biodiversity.
