Abundance and diversity of native bumble bees associated with agricultural crops: The Willamette valley experience

Abstract

There are widespread concerns about declining populations of bumble bees due to conversion of native habitats to agroecosystems. Certain cropping systems, however, provide enormous foraging resources, and are beneficial for population build up of native bees, especially eusocial bees such as bumble bees. In this review, we present evidence of a flourishing bumble bee fauna in the Willamette Valley in western Oregon which we believe is sustained by cultivation of bee-pollinated crops which bloom in sequence, and in synchrony with foraging by queens and workers of a complex of bumble bee species. In support of our perspective, we describe the Oregon landscape and ascribe the large bumble bee populations to the presence of a pollen source in spring (cultivated blueberries) followed by one in summer (red clover seed crops). Based on our studies, we recommend integration into conservation approaches of multiple agroecosystems that bloom in sequence for sustaining and building bumble bee populations. © 2010 S. Rao and W. P. Stephen.