Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/1998
Publication Date: N/A
Citation: Interpretive Summary: INTERPRETIVE SUMMARY Knowledge of the factors impacting populations of native bees is important in acquiring populations of manageable pollinators and in managing these be commercial environments. Unfortunately little is known about the impact o oher environmental factors or exotic bees on native bees. Results of a thr r study at six sites in California suggest that significant differences in umbers between sites and large annual fluctuations within sites are the nor ignificant factors influencing these differences appear to include annual w r patterns, disturbed, fragmented, or isolated habitat, and competition by c bees.
Technical Abstract: ABSTRACT The long-term goal of this study was to use solitary bees to assess the imp f advancing Africanized honey bees (Apis mellifera scutellata Lepeletier) o native California bee fauna. Cavity-nesting, solitary bee species were sy ytically monitored in wooden trap nests at 6 sites in Northern California f 90 to 1992. Three sites were in the San Joaquin Valley in wildlife refuges reserves; 3 were in coastal mountain or Sierran foothill parks or reserves. ferences in frequencies of nesting bees were observed and recorded among si nd habitats through time. A Poisson regression indicated that all explanat ariables and their 1st order interactions were highly significant. There w ignificant differences among bee taxa, sites and years, and their interacti bee x site; bee x year; site x year). Megachile species were the predomina avity nesters in the 3 valley sites; Osmia species were the common group in al mountain/foothill sites. In a computer simulation, using a variation of Poisson regression, several significant differences were also observed betw early frequency counts for certain bee species at the same site. Possible ns for year to year changes included differential natural mortality, extrem ual weather patterns, use of marginal habitats, and negative impacts from e solitary bee species. Three exotic megachilids (Megachile rotundata (F), icalis Spinola, and M. concinna Smith)have successfully invaded and become lished in California. Possibly, M. apicalis has affected other cavity nest ee species, including the exotic M. rotundata in our Central Valley sites.