Here's another reference about interactions between native bees and
introduced honeybees:
Sugden, E. A., and G. H. Pyke. 1991.  Effects of honey bees on colonies of
Exoneura asimillima, an Australian native bee.  Australian Journal of
Ecology 16:171-181.
 
It cites some other appropriate references, including:
Roubik, D. W. 1978.  Competitive interactions between Neotropical
pollinators and Africanized honey bees.  Science 201:1030-1032.
 
Roubik, D. W. 1983.  Experimental community studies:  time-series tests of
competition between African and Neotropical bees.  Ecology 64:971-978.
 
David Inouye
Dept. of Zoology
University of Maryland