Nectar foragers contribute to the pollination of buzz-pollinated plant species

PREMISE OF THE STUDY: Pollination performance may depend on the type of fl oral resource (pollen or nectar) foraged by visitors. In buzz-pollinated plant species, the poricidal anthers release pollen during active pollen collection that induces fl ower vibrations. These buzz-pollinated species generally do not produce nectar. Nevertheless, several Ericaceae are buzz-pollinated and produce nectar. We estimated the relative eff ectiveness of visitors according to the type of resource collected, nectar or pollen (buzzing). M ETHODS: We compared the relative performance of pollen removal, transport, and deposition (eff ectiveness) of the main insect visitors on four ericaceous species: three buzz-pollinated species with diff erent pore sizes, Erica tetralix , Vaccinium myrtillus , and V. vitis-idaea ; and one non-buzz-pollinated species, Calluna vulgaris . KEY RESULTS: Bumblebees were the main pollinators for the three buzz-pollinated species, whereas hoverfl ies were the main pollinators for the nonbuzz- pollinated generalist C. vulgaris . For the studied plant species, we observed no diff erence in pollination eff ectiveness among bumblebee species. Buzzing bumblebees were the most eff ective visitors for pollination per fl ower visit for the two Vaccinium species, whereas nectar foragers were the most eff ective visitors for pollination of E. tetralix . In the case of Vaccinium myrtillus , nectar foragers contributed the most to pollination success because they were more abundant than pollen foragers. C ONCLUSIONS: We showed that consideration of the resource collected by visitors and their behavior is necessary to compare their relative performance. The combination of visitation rate and eff ectiveness per visit reveals that nectar foragers make a substantial contribution to pollination of the buzz-pollinated ericaceous species.