(2nd Place) Role of nesting habitat in specialist bee occupancy of host plant patches

Wild bees require both floral and nesting habitats to persist in an area, and the quality of this habitat is reflected in bee abundance. Nesting habitat is as important as flower resources because bees spend most of their life in the nest. Planting flowers can help bees thrive, but bee populations may be limited by nesting sites and resources for building nests. Therefore, conserving bees requires a good understanding of nesting habitats in addition to floral resources. Studying diet specialist bees in locations that have their host plants presents an opportunity to explore the effect of nesting habitat while controlling for the influence of floral resources. To investigate the importance of both nesting sites and floral resources, we surveyed bee visitors to the host plants of the specialist bees Andrena erigeniae and Melissodes desponsus, and quantified environmental features that may be important for bee nesting including percent bare ground, leaf litter, pebble, vegetation, and deadwood coverage, soil compaction, soil texture, and slope. We assessed the influence of host plant density and environmental factors on specialist bee presence and abundance, and bee richness using generalized linear models and multivariate methods. Andrena erigeniae was detected at 93% of sites with its host plant and associated with a high proportion of leaf litter coverage. Melissodes desponsus was detected at 64% of sites with its host plant and associated with a high proportion of bare ground. The different habitat and environmental associations of these species underscore how habitat diversity can support diverse bee communities.