Evolutionary and ecological processes influence a plant-bumble bee network

Species interactions, such as those between plants and pollinators, are known to be shaped by both evolutionary history and ecological factors. However, the relative importance of neutral- and niche-based ecological processes is still under debate, and little is known about which ecological factors are most important for explaining phylogenetic patterns in interaction networks. Using a plant-bumble bee network comprising 2428 interactions between 29 plant species and 12 bumble bee species in the Himalaya-Hengduan mountains, we tested for phylogenetic signal and whether phylogenetic pattern was explained by 14 plant and four bumble bee ecological traits. We also tested whether trait matching between bumble bee tongue length and flower tube depth explained interaction patterns. All of the measured traits contributed to explaining the phylogenetic attraction pattern, among them, species abundances, nectar volume, and nectar sugar concentration were the most important predictors. Meanwhile, trait mismatch between bumble bee tongue length and flower tube depth failed to predict the interactions, with short-tongued bees generalized across tube depths. Our findings suggest neutral-based process seems to matter more than niche-based processes in this system and help to predict how interactions will respond when key traits are altered by pollinator declines and global change effects.