Pollinator community predicts trait-matching between oil-producing flowers and a guild of oil-collecting bees

The impact of pollinator community diversity on trait-matching in plant-pollinator interactions is poorly studied, even though many mutualisms involve multiple interaction partners. We studied ten communities in which one to three species of oil-collecting Rediviva bee pollinate the long-spurred, oil-producing flowers of Diascia 'floribunda' to examine how pollinator diversity affects covariation of functional traits across sites and trait-matching within sites. Floral spur-length was significantly correlated with weighted grand mean foreleg length of the local bee community but not with foreleg length of individual bee species. The closeness of trait-matching varied among populations and was inversely related to pollinator community diversity. For all bee species, trait-matching was closest at sites characterized by exclusive, pairwise interactions. Reduced trait-matching associated with increased community diversity for individual pollinator species, but close matching at the community level support the importance of community context for shaping interacting traits of flowers and pollinators.