Date of Award
Level of Access
Master of Science (MS)
Ecology and Environmental Sciences
Francis A. Drummond
Second Committee Member
Lois Berg Stack
Third Committee Member
Alison C. Dibble
Additional Committee Members
L. Brian Perkins
Pollination of both wild and crop plants is at a crossroads; honey bee populations are experiencing losses at a higher rate than ever before, and some native bee species are declining in abundance to the point of being listed as endangered species. A few examples of these threats include pesticide exposure, habitat loss, and climate change. In response to bee population declines, conservation efforts have been initiated to increase habitat quality for bees by planting pollinator reservoirs or gardens. Plants provide nutrition to bees in the form of pollen and nectar. Several studies have shown links between higher nutritional quality in pollen and nectar and increased fitness in the following generations of bees.
Our knowledge of bee nutrition has increased dramatically by studying the managed honey bee (Apis mellifera L.) and several species of the commercially available bumble bees, but little is known of the nutritional requirements of wild native bees. In Chapter One I summarized the published literature on managed bee and wild native bee nutrition. A synthesis of this information was used to develop a speculative dissertation on wild native bee nutrition.
Chapter Two presents the results of my research conducted with the objective of determining the role of nutritional quality of pollen and nectar both directly and indirectly on bee visitation to flowers in the field. I hypothesized that pollen and nectar quality, as defined by both amino acids diversity and sugar ratios and concentration, will have a larger effect on bee visitation rates than other floral characteristics. I also hypothesized that an increase in soil fertility would increase pollen amino acid content and in turn bee visitation. I conducted two field experiments to test these hypotheses.
In the first experiment, I observed four bee taxa (Honey bees, all Bumble bees excluding the species Bombus ternarius, the bumble bee species: Bombus ternarius, and all Other Bees) for visitation on four selected plant taxa (Bee’s friend [Phacelia tanacetifolia], Blanket flower [Gaillardia aristata], Borage [Borago officianalis, and Sunflower [Helianthus annuus ‘Zebulon’]) in four locations in Downeast Maine. Floral morphological characteristics and nutritional content of pollen and nectar were measured to determine which characteristics were correlated with bee visitation to flowers. I found that bees in different taxa foraged preferentially on one or several of our selected four species, but pollen amino acids and the floral traits measured were not factors influencing this visitation.
In the second experiment, I varied soil fertility for jewelweed (Impatiens capensis) and measured subsequent floral production, flower morphological characteristics, pollen amino acids, and bumble bee visitation. I found that increased fertilizer did have a positive effect on plant growth, flower production, and amino acid content, which in turn positively influenced bumble bee visitation. The number of open flowers, and not amino acid content, was the consistent predictor of bee visitation to flowers.
Leach, Megan E., "Flower Visitation in Relation to Pollen and Nectar Nutrition: Implications for Pollinator Habitat and Conservation" (2018). Electronic Theses and Dissertations. 2914.