Differentiating nectar from pollen foraging affects estimates of specialization in plant-pollinator networks: a case study from the Bornean peat swamp forest canopy

Abstract Specialization is a core concept in the study of flowering plants and their relationships with floral visitors. In recent decades, researchers have increasingly used bipartite floral interaction networks to study these relationships. Networks are typically built from simple observations of floral visitation and ignore which resources visitors acquire during visits. However, flowers can provide nectar, pollen, or both, and floral visitor species may only forage for one or the other on a given plant. Here, using data we collected which differentiates nectar from pollen foraging for floral visitors to 15 Bornean rainforest tree species, we investigate whether estimates of specialization change when multiple floral resources are accounted for. We find that the same visitors have different estimated values of specialization when calculated using the overall visitation data (the standard approach), versus only nectar or pollen foraging. Differences in specialization estimates for flower-visiting taxa scale up to affect estimates of specialization for the whole community of floral visitors, with greater specialization found in nectar than pollen foraging. Our findings highlight some important considerations when using resource-agnostic visitation data in network-based studies of plant-pollinator relationships. In addition, this study represents one of the first network analyses of plant-pollinator interactions in a tropical rainforest canopy.