Hi all
I think this the following is a clear example of confirmation bias, particularly since it is referring to Southern California, which had an incredible wealth of native bee plants, which were pollinated by native bees, and which provide a boon to beekeepers during wet years. 

I doubt that honey bees have negatively impacted native bee populations anywhere near as much as they have been devastated by human activity. Further, the study of native bee abundance is hampered by the long term droughts that California experiences.

Unfortunately, she cites her own work as proof, and the reference is unavailable for public view.

The balance of evidence suggests that
European honey bees (Apis mellifera) have a
negative impact on native bees and that they
reduce pollination services, decrease the seed
set of native plants, and preferentially pollinate
the flowers of nonnative plants (reviewed in Knapp 2010a).

Monographs of the Western North American Naturalist 7, © 2014, pp. 421–434
ECOSYSTEM RESTORATION ON SANTA CATALINA ISLAND:

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