Ecological patterns of bees and their host ornamental flowers in two northern California cities

A survey of the bee species and their ornamental host flowers that occur in residential neighborhoods of the cities of Albany and adjacent Berkeley in northern California was conducted from 1999-2003. A simple bee frequency (visitation) count was developed to evaluate the relative attraction of bees to their host flowers. Results of the survey revealed that 76 species of bees, mostly natives, from five families, visited 129 host plants at measurable levels. The most common host plant families were Asteraceae, Lamiaceae, Polygonaceae, Rosaceae, and Scrophulariaceae. Honey bees and all other bee taxa were recorded separately on host plants, and both bee groups were more attracted to California native plants than exotics on a percentage basis. Variable attraction was recorded within native and exotic host plants, and a large pan of this variation appears related to where the plants are found in residential areas. In general, the highest bee diversity and abundance was observed in diverse gardens having a high number of bee-attractive plants flowering at the same time. Ground nesting by several species was also noted in diverse and other garden sites. Overall, many bee species seem pre-adapted to use extant urban resources for forage, reproduction and survival in residential areas of these two California cities.