The effects of land use on pollinator community homogenization

Human land-use is homogenizing landscapes around the world. This homogenization leads to decreases in gamma diversity. Such losses in global biodiversity might not be apparent at small scales, but are only detectable when communities of species are evaluated at landscape scales. This kind of landscape scale impact may be playing a role in the decline of insect populations, and in particular, the loss of valuable pollinating insects. Our goal was to determine whether certain types of land use lead to homogenization among pollinator communities in eastern TN. We sampled four plots at each of five different locations (Urban Gardens, Forage Grassland, Mixed Agriculture, Forest, and Organic Farm) for pollinators over the course of six weeks. Each of the twenty plots contained six plant species native to the state of Tennessee, on which we spent 20.83 hours collecting approximately 1,500 specimens. We concurrently sampled the landscape within a 50 m radius of each plot, collecting approximately 3,200 flower-visiting insects during 16.67 hours. Our objective was to determine whether the pollinator communities visiting plants within these experimental plots was a subset of the pollinator community in the surrounding landscape. Within the landscapes sampled, we saw a significant difference in both plant diversity and plant density. We observed the highest plant diversity and insect abundance at the Urban Gardens. Pollinator abundance was higher in the landscape than the plots for four sites, and roughly equal at the Mixed Agriculture site. Our next goal is to compare species richness between the plots and landscapes.