Diet And Diversity: Bumblebee (Bombus spp.) Community Response To Flowering Plant Diversity In Virginia Grassland Meadows

Bumblebees (Bombus spp.) are important pollinators both ecologically and economically. Many bumblebee species have experienced significant declines in both North America and Europe. Habitat loss and fragmentation associated with agricultural intensification are purported causes in several cases. Studies also suggest that reduction of host plant abundance and diversity associated with this type of land use change disproportionately impacts bumblebee species with specialized diets, and that these species tend to be long-tongued. In this study, we examined bumblebee community response to floral resource availability and diversity in grassland meadows throughout the Northern Shenandoah Valley in Virginia, and whether diet breadth (i.e. degree of specialization) and tongue length are correlated among bee species in this region. Between June 5 and Jul 25 of 2011, we surveyed and quantified flowering species in seven grassland meadows for a total of two visits per site. Collections of bees were conducted following each floral survey, and identifications were made on-site. The proboscis (“tongue”) lengths of bumblebees were measured using digital calipers in the laboratory. Preliminary results show that bumble bee species diversity (Shannon Index) is positively associated with floral diversity (Shannon Index) and abundance in meadows (Linear Regression: F = 24.09, p = 0.004, R² = 0.82). Our data also show that bumblebee tongue length is negatively correlated with diet breadth (Spearman’s Rho = -0.83, p = 0.04), revealing that species with longer tongues exhibit specialist tendencies. These preliminary findings demonstrate the importance of resource availability and diversity in fostering diverse bumblebee communities.