Dynamics of species-rich predator-prey networks and seasonal alternations of core species

Using high-throughput detection of prey DNA from spiders in a grassland ecosystem, the authors reconstruct interaction networks between 50 spider species and 974 prey species and strains, documenting shifting seasonal dynamics. In nature, entangled webs of predator-prey interactions constitute the backbones of ecosystems. Uncovering the network architecture of such trophic interactions has been recognized as the essential step for exploring species with great impacts on ecosystem-level phenomena and functions. However, it has remained a major challenge to reveal how species-rich networks of predator-prey interactions are continually reshaped through time in the wild. Here, we show that dynamics of species-rich predator-prey interactions can be characterized by remarkable network structural changes and alternations of species with greatest impacts on community processes. On the basis of high-throughput detection of prey DNA from 1,556 spider individuals collected in a grassland ecosystem, we reconstructed dynamics of interaction networks involving, in total, 50 spider species and 974 prey species and strains through 8 months. The networks were compartmentalized into modules (groups) of closely interacting predators and prey in each month. Those modules differed in detritus/grazing food chain properties, forming complex fission-fusion dynamics of belowground and aboveground energy channels across the seasons. The substantial shifts of network structure entailed alternations of spider species located at the core positions within the entangled webs of interactions. These results indicate that knowledge of dynamically shifting food webs is crucial for understanding temporally varying roles of 'core species' in ecosystem processes.

Automated summary

Using high-throughput detection of prey DNA, the authors reconstructed interaction networks between 50 spider species and 974 prey species, revealing shifting seasonal dynamics. The results show that species-rich predator-prey interaction networks undergo remarkable structural changes, with core species playing significant roles in ecosystem processes.