The out-of-equilibrium dynamics of species

The diversity of natural communities is sustained by a large proportion of rare species. Instead of being less adapted organisms on their way to extinction, they can be involved in the dynamics of complex assemblages, and their contribution to ecosystem function is of increasing concern for researchers. Recent surveys of species-rich communities, together with mathematical models describing a large number of interacting and heterogenous populations, are pointing towards out-of-equilibrium-dynamics, in contrast to fixed competitive hierarchies, as the governing patterns of rarity and abundance.