| dc.description.abstract | Human alterations to landscapes impose novel conditions on native plant and animal species. Exotic plants are among these changes and are presently common and prevalent across Northern Great Plains (NGP) grasslands. Their introductions alter plant communities and influence the wildlife species that rely on the resources provided by plant communities. Exotic plants displace native plant species, but we do not understand how or if some exotic plants can provide resources to pollinating insects requiring floral resources. Considering the spread of exotic plants and the important ecological services bees provide, it is important to understand how native bees value and interact with exotic plants, and how exotic plants may shape bee communities in the NGP. To address this, we employ a unique dataset built from a statewide survey of bees and associated plant species across North Dakota grasslands to investigate the broad questions of how bees select between native and exotic floral resources, how exotic grasses may indirectly affect bee diversity through the plant community, and how exotic species dominance changes the interaction structure between bees and plants. From our selection analyses, we found native bumble bees selected for native plants and plant diversity over exotic plants whenever significant selection occurred, while European honey bees selected for exotic plants and floral resource density. However, both benefited from floral resource diversity, indicating that common management may exist for both groups. Invasive grasses did not affect bee richness at a broad scale but negatively influenced particular bees, such as ground-nesting species. We found litter accumulation to be influential over plant communities and particular types of bees based on their life history traits, indicating the need for grassland management practices that prevent homogenous plant structure. Finally, we found that exotic bees and plants influenced bee-plant interaction network properties through their dominance over contemporary pollination networks. This implicates that managing exotic species may be needed to reduce effects on the complex bee-plant interactions and consequent pollination services. Broadly, this work provides further evidence of exotic species effects on ecological communities and the first large-scale assessment of their impacts on bee communities in NGP grasslands. | en_US |
