Despite large interest in dispersal and disturbance as drivers for coexistence of species and maintenance of species diversity patterns, much remains unknown about the interaction between both processes. Particularly support from natural systems remains deficient. We have used an invertebrate metacommunity residing in a cluster of temporary freshwater rock pools with variable sizes and flooding regimes as a model system to study effects of disturbance regime (flooding regime) and dispersal (pool isolation) on within patch coexistence of invertebrates with different dispersal modes. Flooding regime (frequency and duration) of pools was characterised using a hydrological model. Direct dispersal measurements confirmed the presence of a dispersal gradient.
Results/Conclusions
For passive dispersers the effect of dispersal on species coexistence depended on disturbance regime. The hump shaped dispersal-coexistence pattern as predicted by mass effects models was only detected in highly disturbed ephemeral pools. This is indicative of a much higher impact of dispersal on communities subject to intensive disturbance regimes than on communities experiencing a more stable environment. In contrast, pool isolation and disturbance did not affect coexistence of active dispersers, subscribing the importance of dispersal mode as a determining factor for metacommunity structure. Furthermore, our results also support model predictions that high dispersal rates of a dominant competitor, in this case fairy shrimp (Anostraca - Crustacea), may explain mass effects patterns. A better integration of the link between disturbance regime of patches and the translation of dispersal into species establishment in current metacommunity models may help to increase our understanding of the maintenance of diversity in heterogeneous landscapes at multiple spatial scales.
