Ecosystem development theory predicts that successional turnover in community composition can influence ecosystem functioning. However, tests of this theory in natural systems are made difficult by a lack of independent replicates. Using the microbial digestive associates of a carnivorous pitcher plant, I tested hypotheses linking age-driven microbial succession to host functioning. Monitoring the yearlong development of independent digestive communities in two pitcher plant populations revealed a number of trends in community succession matching theoretical predictions. These included mid-successional peaks in bacterial diversity and metabolic substrate use, predictable and parallel successional trajectories among leaf communities, and convergence giving way to divergence in community composition and carbon substrate use. Bacterial composition, biomass, and diversity positively influenced the rate of prey decomposition, which was in turn positively associated with a host leaf's nitrogen uptake efficiency. These results highlight links between community succession and ecosystem functioning and extend succession theory to host-associated microbial communities.