Hawaiian Hylaeus (Hymenoptera: Colletidae): potential pollinators in the Pacific?

Bees (Apoidea) are well known pollinators of numerous managed and unmanaged flowering plants. Of the ~20,000 described species of bee, only 60 species are found in the Hawaiian Islands, all belonging to the cosmopolitan genus Hylaeus (Hymenotpera: Colletidae). Hylaeus are typically not considered to be effective pollinators of flowering plants due to their lack of plumose hairs and corbicula. In this study we quantified pollen loads on the external surfaces of Hawaiian Hylaeus and describe their foraging behaviors inside the flowers of the endemic Vaccinium reticulatum (Ericaceae). We found that Hawaiian Hylaeus are capable of transporting low levels of pollen on external surfaces of their bodies and may be capable of facilitating dehiscence in the poricidal anthers of V. reticulatum. We review what is known about “buzz pollination” by species of the genus Hylaeus, with special attention on Hylaeus found in the Pacific, and discuss their potential as pollinators of native Hawaiian plants. Considering the urgency of biodiversity conservation in the Hawaiian Islands, we advocate for further research on the foraging ecology of Hawaiian Hylaeus and the reproductive biology of the plants they visit for pollen and nectar resources.