Abundant top predators increase species interaction network complexity in northeastern Chinese forests.

Species interactions remain a cornerstone in shaping community dynamics and structure, alongside other factors, such as climate conditions and human activities. Although network structure is known to influence community stability and ecosystem functioning, the roles of top predators in shaping interaction network structure remain obscure. We examined a 5-7-year time series of species detections for mammal communities in multiple protected areas to investigate the association between top predators and interaction network structure. Our findings suggest that abundant species, day-active species and species with wide habitat breadth interact with more species, as did species that were more affected by vehicle disturbance. With increased densities of top predators, interaction networks exhibited greater complexity, with increased connectance, nestedness and average degree. An increased density of mesopredators, such as yellow-throated martens and badgers, was associated with sparser, less nested, but more centralized interaction networks. Top predators reduced the degree of highly interactive species, making them more specialized, and increased the degree of less abundant species, making them more general. In particular, this redistribution of interactions was not driven by direct changes in species density of top predators but seemingly by non-consumptive or indirect effects. Our findings emphasize the pivotal role of the main predators in structuring interactions within northeastern China's mammal communities, with large implications for conservation and management.