Bee pollen under the microscope : The significance of classical morphological methods and its pro’s and con’s

The populations of wild pollinators have been declining worldwide, mainly due to habitat loss or change. Some farmers use honeybees to secure pollination of their crops, but honeybees can cause further problems effecting wild pollinators. Knowledge of foraging plants for honeybees can give a clue to the conditions of interactions and competition between honeybees and wild pollinators. The aim of this study was to identify plants visited by honeybees, and to compare classic morphological methods of identifying pollen to other modern palynological techniques. Samples of bee pollen from two hives in Västerbotten county, Sweden, was studied with light microscope. A selection of the samples were also studied in scanning electron microscope or by extraction of nucleic acid followed by PCR. All the identified pollen types originated from plants common in Sweden, for example, raspberry, rosebay willowherb, member of the genus Vaccinium and different types of clover. Due to similar morphology, many of the pollen types had more than one possible origin. Many types of pollen found in the samples remained unidentified. Regarding modern palynological techniques, one grain of bee pollen was substantial to extract enough nucleic acid to perform PCR. Positive PCR reactions were found for all but one of the seven PCR primers tested. Each primer gave positive reaction to only one color of bee pollen. One of the colors of bee pollen did not give any positive PCR reaction. The result of this study highlights the further need of reliable and available reference material in the palynological field