Time-variant species pools shape competitive dynamics and diversity-ecosystem function relationships in pitcher plant bacterial communities
Biodiversity-ecosystem function (BEF) experiments often employ common garden designs, drawing samples from a local biota. However, the communities from which taxa are sampled may not be at equilibrium. I assembled pools of aquatic bacterial strains isolated at different time points from leaves on the pitcher plant Darlingtonia californica to evaluate the role of a dynamic, host-associated microbiota on the BEF relationship. I constructed experimental communities using bacteria from each time point and measured their respiration rates. Communities assembled from mid-successional species pools showed the strongest positive relationships between community richness and respiration rates, driven primarily by linear additivity among isolates. Diffuse competition was common among all communities but greatest within mid-successional isolates. These results demonstrate the dependence of the BEF relationship on the temporal dynamics of the local species pool, implying that ecosystems may respond differently to the addition or removal of taxa at different points in time during succession.