Determinants of species' centrality in spatially-connected plant-frugivore networks

Abstract

Species' characteristics, such as their capacity to disperse great distances or to interact with many partners, may determine their ability to propagate impacts within and across communities. These spatial and interaction-related processes may have synergistic or opposing influences on a species' ability to connect with others, but typical analyses of ecological networks may not be able to disentangle these effects. Here, we explored how the way in which a plant–frugivore metanetwork is described influences our perception of the species that can most impact others via direct and indirect effects. Specifically, we tested whether the ranking of bird species' centrality and its relationship with species' characteristics depend on whether spatial distance and dispersal constraints are depicted in the metanetwork. To do this, we described a metanetwork comprising 29 local frugivory networks from the Atlantic Forest and Cerrado subrealm of Brazil using a gradient of spatial information, from simply aggregating interaction data across sites to using multilayer networks that connect populations from spatially-separated communities according to their spatial distance and species' dispersal capacities. We found that rankings of bird species' centrality were, on average, not strongly influenced by incorporating spatial and dispersal effects (versus aggregating interaction data across sites), though the centrality of individual species changed considerably in some cases. Three species-level characteristics, degree of frugivory (which is associated with interaction generalism), area of habitat (which is associated with the number of local networks in which a bird species occurs) and body mass predicted bird species' centrality consistently across the different approaches used to generate the metanetwork. Our findings indicate that key characteristics associated with spatial and interaction-related processes can determine the central role of species in spatially-connected interaction networks, irrespective of whether spatial and dispersal constraints are explicitly incorporated in the metanetwork.