The effects of dispersal and river spatial structure on asynchrony in consumer–resource metacommunities

Abstract

Abstract River network structure influences many important population and community processes. Previous work examining ecological dynamics in river networks has focused on within‐trophic‐level dynamics, with less emphasis on food‐web interactions. Yet, trophic interactions in rivers are influenced by processes that may interact with network structure and position. Using a spatially explicit consumer–resource model, we explore how trophic dynamics are influenced by the branching nature of river networks. We focus on cases where the consumer–resource interaction is prone to temporal oscillations and periodic low population sizes. In these cases, we find that the influence of network structure and dispersal can reduce temporal variability and increase persistence of consumers and resources at the metacommunity scale. The effects of network structure and dispersal on our observed metacommunity dynamics result from asynchrony among dynamics of local communities: when asynchronous local fluctuations are averaged, consumer–resource dynamics become less variable and bounded higher above zero at regional spatial scales. Fluctuations synchronise across clusters of linked local communities. Communities that connect to only one other downstream community typically vary independently of other patches and show high variability, while communities that are linked to multiple upstream and downstream habitats show greater clustering and less variability. These patterns suggest that headwater versus mainstem locations in river networks may show different levels of population variability and thus differential responses to management and restoration efforts.