Functional diversity drives plant-bee specialization in tropical forests

Understanding how species traits shape ecological interactions across organizational levels is fundamental to explaining tropical biodiversity. In plant–pollinator systems, competition, niche partitioning, and specialist–generalist strategies are closely linked to functional trait variation, which can influence species coexistence and network structure. Yet, how the functional diversity of interacting groups determines network organization remains poorly understood, particularly in pristine tropical forests. Here, we examined how plant and bee functional diversity structures plant–pollinator interaction networks in a pristine Amazonian forest. Specifically, we evaluated whether functional richness, evenness, and dispersion of plants and bees influence interaction diversity, interaction evenness, network specialization, and connectance, and whether species traits predict species-level specialization. Higher bee functional richness was associated with lower network specialization, suggesting that a broader range of pollinator traits promotes more generalized interaction patterns. In contrast, greater plant functional dispersion and higher bee functional evenness were associated with reduced connectance, indicating that trait differentiation among plants may promote niche partitioning, whereas an even distribution of pollinator functional traits may redistribute interactions among functionally similar species. Solitary bees showed higher specialization than social bees, highlighting their potential importance for the reproduction of plant species with specific pollination requirements. Overall, our findings show that functional trait diversity shapes plant–pollinator network organization at both community and species levels. By integrating functional traits into interaction network analyses, this study advances understanding of the mechanisms supporting niche partitioning, functional redundancy, network robustness, and ecosystem functioning in highly diverse tropical forests.