A General Unified Niche-Assembly/Dispersal-Assembly Theory of Forest Species Biodiversity

A generalised niche-assembly/dispersal-assembly theory is outlined. The aim is an explanatory theory of island/sample species abundance curves, of species-area curves, and of island biogeography phenomena. A niche space is defined over a spatial domain in terms of, for example, a stratification obtained from an environmental variable defined over that domain. Within each niche a neutral individual behaviour model is adopted (i.e. species-independent). Individual mortality is random and replacement is stochastic, depending on local species density per niche. A general formulation of a spatial model of stochastic inter-niche (seed) dispersal is presented; a Markovian inter-niche dispersal probability matrix is introduced. By stages, a simple spatially symmetric model of dispersal is defined which is neutral within niches, but not inter-niche neutral. Finally, this may be reduced to a distance-independent niche-dispersal (1 order) model which is essentially a simplest “truly unified model” (Hubbell (2001, p319) which generalises Hubbell’s “unified theory” (the 0 order model).