2018 Update: Bees remove and deposit pollen

This year in experimental plot 2, we measured pollinator visitation rates, per visit pollen removal, and per visit pollen deposition across common pollinator taxa to provide insight into pollination failure in Echinacea. We collected male and female phase floret samples from 183 Echinacea head observations conducted from July 9^th to the July 31^st, 2018. The pollinator taxa included in analysis were Andrena (N=18), Augochlorella (N=9), male Melissodes (N=53), small black bees (N=59), and unvisited heads used as environmental controls (N=30). Using light microscopy, we then quantified the number of pollen grains in these samples to determine how much pollen an individual of each taxon removes and deposits per visit. We found that the composite specialist Andrena rudbeckiae removes more grains of pollen per visit than the other common pollinator taxa in the study area; namely, male Melissodes sp., Augochlorella sp., and ‘small black bees,’ a wide taxonomic group comprising a variety of species mostly in the Halictidae. Pollen limitation in the population could be driven by frequent male Melissodes sp. visitation late in the season; based on the per visit removal of male Melissodes sp. and number of visits observed in this study. These results combine to contribute to our understanding of pollination failure and pollen limitation in small fragmented flowering plant populations.