Effects of asymmetric dispersal on the coexistence of competing species.

The global biodiversity crisis has made a priority of understanding biodiversity maintenance in ecological communities. It is increasingly apparent that dispersal patterns can have important effects on such maintenance processes. Nevertheless, most competition theory has focused on a small subset of the possible dispersal patterns in nature. Here, we show that spatially asymmetric dispersal, i.e. the disproportionate transport of propagules towards or away from particular habitat patches in a metacommunity, when it differs between species, can promote the coexistence of competing species even in the absence of environmental heterogeneity among habitat patches. Moreover, when asymmetric dispersal is present, changes in the self-recruitment of competitive dominants and subordinates have important, but fundamentally different, effects on species coexistence. Our results underscore the importance of the interplay between species interactions and dispersal patterns for understanding the effects of habitat fragmentation and for designing regional-scale conservation strategies, such as networks of protected areas.