Species traits and landscape structure can drive scale-dependent 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 partly because the species traits and landscape structures allowing indirect effects to propagate may differ across scales. Here, we use a topological network metric, communicability, to explore the factors controlling spatial propagation of effects in a large-scale plant-frugivore network projected across the territory of Aotearoa New Zealand. We show that generalism, species prevalence, and morphological traits are important predictors of species' capacity to propagate effects, but their importance differed across scales. Furthermore, native bird species (but not exotics) show a positive relationship between body size and their potential to propagate effects. Habitat composition is the most important landscape factor in our study, generating hotspots of effect propagation around forested areas, whereas landscapes containing a variety of habitats act as a buffer against propagation. Overall, our results indicate that species displaying specific sets of traits, including ubiquity, interaction generalism, and a combination of large body size and native status, are the most likely to propagate large-scale ecological impacts in the plant-frugivore communities studied, yet landscape properties may moderate this spread.