Habitat alteration by cheatgrass (Bromus tectorum) invasion or revegetation to crested wheatgrass (Agropyron cristatum) has created extensive expanses of monotypic grasslands throughout the Great Basin. In 2006, we installed 36 malaise traps across 3 sites to compare species diversity of bees (Apoidea) between pinyon/juniper (Juniperus osteosperma/Pinus edulis - P. monophylla), sagebrush (Artemisia tridentata), crested wheatgrass, and cheatgrass habitats. The difference in bee diversity between the exotic grasslands and neighboring stands of extant pinyon/juniper and sagebrush is striking. Pinyon/juniper habitat supports a much more abundant bee density than any of the other three habitat types studied. Species richness is also higher in pinyon/juniper but only slightly higher than sagebrush. Bee diversity was significantly different between all habitats with crested wheatgrass having the least bee diversity. Bee diversity was strongly correlated with flowering plant diversity. Even though pinyon/juniper had low plant cover, flowering plant diversity was significantly higher than any other habitat. Considering the important service bees provide as pollinators, maintaining areas of high bee abundance and diversity is important for maintaining the seed banking potential of insect pollinated plants, in effect contributing to community resilience and integrity.