Influences of floral abundance, richness, and spatial distribution on urban garden bee communities
Physical and Biological Sciences
Senior Thesis
Resource distribution strongly shapes ecological communities. For bees, spatial distribution of floral resources may influence foraging efficiency and population persistence, and thus pollinator communities and conservation. In urban landscapes, gardens provide refuges for bee biodiversity, and depending on local and landscape features, such as the distribution of floral resources, urban gardens may be managed to support bee conservation. We examined whether the abundance, richness, spatial distribution of floral resources within urban gardens influence bee abundance (overall and for common species), species richness, and diversity. We sampled bees using aerial surveys and pan traps, and assessed floral abundance and spatial patterns within 19 urban gardens in the California central coast. We included other local and landscape variables that influence urban bees as additional explanatory factors. We found that floral abundance and spatial distribution, as well as landscape surroundings of the gardens all correlate with different components of bee communities in urban gardens. Bee abundance and honeybee (Apis mellifera) abundance negatively correlated with urban land cover surrounding the gardens. Honeybee abundance increased in sites with less clustered floral resources, whereas bee species richness and bee diversity increased in sites with more clustered floral resources. Surprisingly, bee species richness and diversity decreased in sites with very high floral abundance, potentially due to interactions with honeybees. Others have documented the importance of floral abundance and landscape surroundings for bees in urban gardens, but this study is the first to document that the spatial arrangement of flowers strongly predicts bee abundance and richness. Based on these findings, it is likely that garden managers may promote bee conservation by managing for floral connectivity and abundance within these ubiquitous urban habitats.
