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Bees in urban landscapes: An investigation of habitat utilization

  • Author(s): Wojcik, Victoria A.
  • Advisor(s): McBride, Joe R
  • et al.
Abstract

Bees are one of the key groups of anthophilies that make use of the floral resources present within urban landscapes. The ecological patterns of bees in cities are under further investigation in this dissertation work in an effort to build knowledge capacity that can be applied to management and conservation.

Seasonal occurrence patterns are common among bees and their floral resources in wildland habitats. To investigate the nature of these phenological interactions in cities, bee visitation to a constructed floral resource base in Berkeley, California was monitored in the first year of garden development. The constructed habitat was used by nearly one-third of the locally known bee species. Bees visiting this urban resource displayed distinct patterns of seasonality paralleling those of wildland bees, with some species exhibiting extended seasons.

Differential bee visitation patterns are common between individual floral resources. The effective monitoring of bee populations requires an understanding of this variability. To investigate the patterns and trends in urban resource usage, the foraging of the community of bees visiting Tecoma stans resources in three tropical dry forest cities in Costa Rica was studied. Substantial variability was noted between individual T. stans resources in each of the three populations. The observed variability is driven by the quality of the food resource as measured by the number of individual flowers available. Additionally, the regional landscape plays a role in general species occurrence patterns at a resource.

The urban landscape presents a heterogeneous mosaic patchwork of habitat resources. To investigate the influence of this local variability on resource usage, the foraging patterns of bees in tropical and temperate landscapes were examined. In the dry forest of Costa Rica, bee foraging on T. stans was studied in the cities of Bagaces, Cañas, and Liberia. In the coastal grassland region of California, bee foraging on California poppy (Eschscholzia californica) was studied in the cities of Berkeley, Emeryville, and Oakland. In both regions, resource abundance and spatial distribution were the main drivers of bee visitation in all taxon groups. Land use and uniquely urban landscape variables influenced the occurrence of certain bee taxa.

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