Pollination strategy of Hedysarum scoparium Fisch et Mey (Fabaceae) in a dry habitat measured with pollination effectiveness and pollinator importance

Hedysarum scoparium is an important xerophyte in the desert region of north-west China and can grow well as a pioneer plant in shifting sand dunes. Flowers of H. scoparium provide late season pollen and nectar for several insect groups. Hedysarum scoparium benefits from insect pollination in order to set fruit, but it is unknown which flower-visiting insects are the most effective pollinators. In this study, we characterized the pollination effectiveness and the importance of visitors toward flowers of H. scoparium in the middle of Hexi Corridor region, China. Our observations suggest that bees were the most frequent pollinators of H. scoparium: 97% of the visits were made by bees. Individuals of three medium size bee taxa (Apis mellifera, Megachile spp., Amegilla spp.) accounted for 94% of all visits. Pollen grains deposited per visit by bees showed equal effectiveness. Of all the bee groups observed, introduced A. mellifera was potentially the most effective pollinator since it frequent visitors, and had the highest ‘importance value’ followed by Megachile spp., Amegilla spp. Visits by these medium size bees may therefore be important for ensuring H. scoparium fruits set.