Species diversity in neutral metacommunities: a network approach

ABSTRACT

Biologists seek an understanding of the processes underlying spatial biodiversity patterns. Neutral theory links those patterns to dispersal, speciation and community drift. Here, we advance the spatially explicit neutral model by representing the metacommunity as a network of smaller communities. Analytic theory is presented for a set of equilibrium diversity patterns in networks of communities, facilitating the exploration of parameter space not accessible by simulation. We use this theory to evaluate how the basic properties of a metacommunity – connectivity, size, and speciation rate – determine overall metacommunity γ-diversity, and how that is partitioned into α- and β-components. We find spatial structure can increase γ-diversity relative to a well-mixed model, even when θ is held constant. The magnitude of deviations from the well-mixed model and the partitioning into α- and β-diversity is related to the ratio of migration and speciation rates. γ-diversity scales linearly with metacommunity size even as α- and β-diversity scale nonlinearly with size.