At what scales does aggregated dispersal lead to coexistence?
Aggregation during dispersal from source to settlement sites can allow persistence of weak competitors, by creating conditions where stronger competitors are more likely to interact with conspecifics than with less competitive heterospecifics. However, different aggregation mechanisms across scales can lead to very different patterns of settlement. Little is known about what ecological conditions are required for this mechanism to work effectively. We derive a metacommunity approximation of aggregated dispersal that shows how three different scales interact to determine competitive outcomes: the spatial scale of aggregation, the spatial scale of interactions between individuals, and the time-scale of arrival rates of aggregations. We use stochastic simulations and a novel metacommunity approximation to show that an inferior competitor can invade only when the superior competitor is aggregated over short spatial scales, and aggregations of new settlers are small and rare.