Patterns of vegetation biodiversity: the roles of dispersal directionality and river network structure

This paper investigates the importance of dispersal directionality and river network structure to biodiversity patterns. Our model results suggest that dispersal directionality plays a crucial role in determining biodiversity patterns, even more so than dispersal rates. Dispersal directionality heterogenizes the spatial distribution of abundance, which results in higher extinction rates of rare species and higher beta diversity. It induces a few species with very high abundances at the expense of many species with intermediate abundances, thereby lowering alpha and gamma diversities. The river network structure also increases beta diversity, i.e., more heterogeneous ecosystems, in comparison to typical two-dimensional landscapes. We find that the interplay between the dispersal directionality and network topology has important consequences on relative species abundance patterns and the distribution of alpha diversity.