Density dependence explains tree species abundance and diversity in tropical forests

Publisher Website
Google Scholar
Abstract
The recurrent patterns in the commonness and rarity of species in ecological communities—the relative species abundance—have puzzled ecologists for more than half a century1,2. Here we show that the framework of the current neutral theory in ecology3,4,5,6,7,8,9,10 can easily be generalized to incorporate symmetric density dependence11,12,13,14. We can calculate precisely the strength of the rare-species advantage that is needed to explain a given RSA distribution. Previously, we demonstrated that a mechanism of dispersal limitation also fits RSA data well3,4. Here we compare fits of the dispersal and density-dependence mechanisms for empirical RSA data on tree species in six New and Old World tropical forests and show that both mechanisms offer sufficient and independent explanations. We suggest that RSA data cannot by themselves be used to discriminate among these explanations of RSA patterns15—empirical studies will be required to determine whether RSA patterns are due to one or the other mechanism, or to some combination of both.