The title of a 2001 monograph and theory by American ecologist Stephen B. Hubbell (1942– ) that aims to explain the diversity among species (biodiversity) and the relative abundance of species within ecological communities. The theory is neutral in that it supposes that all individuals of a species behave in the same way and that all species behave (i.e. reproduce and die) in the same way. Thus all species and all individuals are equivalent. Provided they all observe the same rules, species can compete and cooperate, but predation and parasitism (see parasite) are forbidden. The theory applies to communities of trophically similar species with a fairly constant population density that are thrown together by chance, history, and random dispersal. It is unified because mathematically the theory can predict the diversity of many different types of community and the spatial relationships governing distribution within communities.
Subjects: Ecology and Conservation.