Dynamics of interaction networks and species' contributions to community-scale flexibility

Architecture of species interaction networks is a key factor determining stability of ecological communities. However, the fact that ecological network architecture can change through time is often overlooked in discussions on community-level processes despite its theoretical importance. By compiling a time-series community dataset involving 50 spider species and 974 Hexapoda prey species/strains, we quantified the extent to which architecture of predator-prey interaction networks can shift across time points. We then developed a framework for finding species that could promote flexibility of interaction network architecture. Those "network coordinator" species are expected to promote persistence of species-rich ecological communities by buffering perturbations to communities. Although spiders are often considered as generalist predators, contributions to network flexibility varied greatly among species. We also found that detritivorous prey species can be cores of interaction rewiring, dynamically interlinking below-ground and above-ground community dynamics. Analyses of network coordinators will add a new dimension to our understanding of species coexistence mechanisms and provide platforms for systematically prioritizing species in terms of their potential contributions in ecosystem conservation and restoration. Significance StatementLike networks of human relations, webs of interactions between species are dynamically restructured through time. By compiling time-series time-series dataset including > 1,000 species/strains, we quantified the magnitude of ecological network dynamics in the wild. The analytical framework developed in this study highlighted "network coordinator" species, which are keys to conserve and restore endangered ecosystems.