Spatial aggregation and the species-area relationship across scales

► We introduce a simple phenomenological model based on Poisson cluster processes. ► The shape of the Species-Area Relationship is linked to the RSA and the beta-diversity. ► We derive an analytical expression for the SAR which reproduces tri-phasic behavior. ► We find an expression for the endemic area relationship and for the scaling of the RSA. ► The model allows one to understand the necessary (geometrical or biological) mechanisms at the core of the observed macroecological patterns.