Document: NEA-3-48-10

Nectar requirements affect pollen foraging of a solitary bee: Exploration using linear-programming models.

WILLIAMS, N.M.*

University of Calgary, Calgary AB, Canada ¹

Abstract:
For herbivores, the need to obtain complementary essential nutrients can favor feeding on mixtures of plant species. Mixing is favored in cases where the distributions or harvesting efficiencies of essential nutrients are inverted among plant species. In natural populations, females of the solitary bee Osmia lignaria provisioned offspring on mixtures of pollen from Salix spp. and Hydrophyllum capitatum, which grew in discrete patches hundreds of meters apart. Females nesting in either patch flew the extra distance between patches and mixed pollen of the two species. Mixing cannot be explained by complementary pollen nutrients because in feeding trials larvae grew equally well on either species alone. Pollen and nectar also are complementary essential nutrients for bees. Osmia lignaria females require pollen and nectar continuously during construction of provisions. I used linear-programming models to explore whether the need for nectar in addition to pollen could explain pollen mixing by female O. lignaria. Pollen and nectar collection efficiencies are inverted between Salix and Hydrophyllum. Bees collect pollen faster at Salix, but collect nectar faster at Hydrophyllum. The model that incorporated only pollen requirements predicted pollen collection from only one plant species, nearly always Salix. When requirements for nectar and pollen were included, the model predicted mixing. Quantitatively, the model agreed with the observed pollen mixing throughout the season by bees nesting at all distances from the resources; however, the predicted and observed effects of distance to a resource showed inverted trends.

Keywords: foraging, linear-programming model, pollen, nectar, resource mixing, solitary bee, Osmia

This abstract is being presented at: 9:15 AM in session:
Oral Session #4: Herbivore Responses to Plants.