Bee diversity in planted grasslands on South Dakota, USA

Bees (Insecta: Hymenoptera: Apoidea) are the pollinators of c. 70% of all flowering plants and are considered keystone organisms in most ecosystems. During the last decade the US Fish and Wildlife Service has been working on the reconstruction of natural ecosystems on severely perturbed sites (ex-farmland, grazing lands, etc.) in the northern Great Plains. The goal of this study was to determine changes in bee diversity through successional changes on planted grasslands in east-central South Dakota. Nine sites were surveyed representing 1, 2, and 3-year old plantings (2009, 2010, and 2011). Each site was sampled six times between June and August of 2012. Bees were sampled using white, blue and yellow pan traps and blue and yellow vane traps. All traps were set around 0800 hours and retrieved around 1600 hours on each sampling day. Bee samples were preserved in 80% ethanol and returned to the lab for processing at the Severin-McDaniel Insect Research Collection at SDSU. Standard taxon diversity and richness indices were calculated using the statistical package PAST version 2.17b (University of Oslo). Nine hundred and twenty bees representing 5 families (Andrenidae, Apidae, Colletidae, Halictidae, Megachilidae) and 61 species were collected. The sites planted in 2010, had the highest index values for richness and diversity among all sites, while the least diverse site was planted in 2011. Blue traps collected 64% of all bees. It is recommended to collect samples of flowering plants along the sampling days because floral resources available influence bee populations more directly.