Canopies drive the reassembly of pollinator communities and interaction networks along tropical forest succession

Abstract Vertical stratification is a prominent driver of forest biodiversity. As canopy cover is lost rapidly worldwide, it is crucial to understand the role of stratification in maintaining and restoring key ecological processes during forest succession, such as pollination. Within a well-resolved recovery chronosequence in the northwestern Ecuadorian rainforest, we compiled an extensive database of over 20,000 diurnal and nocturnal pollinators and 2,000 interactions with plants and examined the interacting effects of recovery age and stratification on pollinator community recovery and interaction network reassembly. Stratification was a stronger predictor of pollinator abundance, alpha-diversity, functional richness, and beta-diversity than forest legacy (successional vs. old-growth). While most groups were strongly associated with canopies (moths, social bees, and nocturnal bees), orchid bees exhibited an inverse pattern. Across the entire chronosequence (0–38 years of recovery, plus old-growth forests), recovery status and stratification had significant, but group-dependent, effects on pollinator abundance and diversity. Interaction networks were most diverse and distinct in canopies, and the highest pollinator and interaction diversity was found in old-growth canopies. In successional forests, networks were comparable in size to active disturbance and early recovery only when both strata were combined. The largest and most generalized networks were found in well-connected old-growth forests, which harbored twice as many interactions as in other recovery stages when both strata were combined. Our study underlines the importance of stratification in supporting pollinator diversity during tropical forest succession and highlights the role of old canopies in safeguarding a diverse pool of pollinator species.