Ecological networks, such as food webs, mutualist webs, and host-parasite webs, are reorganizing as species abundances and spatial distributions shift in response to environmental change. How this reorganization plays out will depend on whether species can access new and suitable habitats as the environment changes and how they interact with other species in the landscape. Species interactions, such as competition, facilitation, and predation contribute to this reorganization by preventing species from optimally tracking their optimal environmental conditions by shifting their distributions. Species interactions and dispersal limitation are generally considered to contribute independently to ecological network reorganization, but theory for competitive interactions suggests that the effect of species interactions should depend on dispersal.
Here we use a metacommunity model to develop new theoretical expectations for how complex networks, comprised of competitive, mutualistic, and trophic interactions, will reorganize under environmental change. We ask how changes in the average rate at which species disperse between habitats affects the degree to which species interactions cause ecological networks to reorganize under long term environmental change (e.g. climate warming).
We find that dispersal is crucial for determining the degree to which networks will retain their composition and structure. When dispersal between habitat patches is low, all types of species interactions act as a strong determinant of whether species can colonize suitable habitats; this colonization resistance drives species turnover, which breaks apart current networks and leads to the formation of new networks. However, when dispersal rates are increased, colonists arrive in high abundance in habitats where they are well suited, so interactions with resident species contribute less to colonization success. High rates of dispersal ensure that species associations are maintained as they shift in space, so networks retain similar composition and structure. The crucial role of dispersal reinforces the importance of managing habitat connectivity to sustain species and interaction diversity into the future.