Background/Question/Methods Seed dispersal mutualisms play a fundamental role in structuring diverse communities of plants and animals in tropical forests. Representing such mutualistic communities as complex networks is now widely applied to analyze how interaction patterns among species are linked to biodiversity and stability within communities. Despite the universal recognition of spatio-temporal variation in biodiversity, only recently has this complexity been considered in plant-frugivore networks. We conducted a study to: (1) quantify temporal turnover in species and their interactions through time to evaluate spatio-temporal variation in network properties; (2) evaluate the drivers of relative functional importance of species in networks; and (3) test whether competition or facilitation influence temporal variation in network topology. To answer such questions, we sampled local frugivore networks in six communities in the central Dominican Republic continuously over a full annual period (May 2018 – May 2019), visiting each site every 2–3 weeks (n= 21 visits) to conduct fruit and bird surveys, followed by focal observations of plants to quantify interaction frequencies. Results/Conclusions We recorded 7,697 frugivory events involving 44 avian species and 53 plant taxa and found that local networks tended to remain consistently and nonrandomly nested across time, despite persistent changes in community composition and rewiring of species interactions. Phenophase of birds and plants was the strongest determinant of the functional importance of species within networks. We found significant multilayer modular structure in all six local networks with a consistent exclusionary pattern, in which taxa belonging to the same guild were less likely to co-occur within modules than expected by random chance. These results suggest competition and temporal niche partitioning as likely mechanisms structuring plant-frugivore networks. Our results provide important insight into how short-term, seasonal dynamics shape communities and provide empirical evidence for competition rather than facilitation as the major driver of temporal plasticity in mutualistic networks.
