Niche partitioning is one of the key mechanisms allowing species co-existence and is especially relevant in species-rich communities. For pollinators, morphology is a major axis in which species differentiate their foraging niche, as it influences the match with flower morphology. Bumblebees (Bombus spp.) are important pollinators globally, showing their highest diversity of co-occurring species in the Hengduan Mountains region of southwestern China. This community context makes the region an ideal model system to test the importance of niche partitioning for plant-pollinator interactions. In high-elevation flower-rich meadows, over four years, we sampled pollinator-plant interaction networks containing 12 sympatric bumblebee species, varying more than fourfold in tongue length from 4.7 to 21.7 mm. We then assessed the degree of niche partitioning occurring between these bumblebees. We analysed bumblebees’ foraging niche widths and overlap and found that species with longer tongues foraged from a narrower range of flowers. Accordingly, bumblebee species having shorter tongues and visiting a higher diversity of flowering species also showed consistently higher floral overlap with other bumblebee species across years. In spite of this morphology-driven niche pattern for species, the interaction network was consistently characterized by high generalization across the years. Our results indicate that the co-occurrence of a large number of potentially competing pollinators with high generalization and niche overlap is possible in flower-rich habitats. We suggest that, in regions of extraordinarily high plant and pollinator diversity and abundance, diverse pollinator communities may also be maintained without strong foraging niche partitioning.

Our dataset was built by pooling together all bumblebees visiting flower information available for the Yulong Snow Mountain from 2016 to 2019.