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 communit...