Species traits and community structure can drive large-scale spatial propagation of effects in ecosystems

Species can directly and indirectly affect others across communities and habitats, yet the spatial scale over which such effects spread remains unclear. This uncertainty arises in part because the species traits and landscape structures allowing indirect effects to propagate may differ across scales. Here, we introduce a topological network metric, communicability, to explore how indirect effects propagate across space in simulated metacommunities and in a large-scale plant-frugivore network across the territory of Aotearoa New Zealand. We show that generalist birds and plants spread indirect effects efficiently at the local scale, whereas a widespread distribution further allowed species to propagate effects across the landscape. Habitat composition, rather than arrangement, was the most important landscape factor in our study, generating several hotspots of effect propagation around forested areas. Overall, our results indicate that generalist and widespread species, two characteristics associated with species invasions, are the most likely to propagate large-scale ecological impacts.