I, an interested non-expert, have been following this thread with
bemusement.

My untutored self says to my better judgment that it's probably not
competition among the pollinators at all.  Rather, has anyone considered
that loss of range, particularly mixed plant species range, is what's
harming the native insects?  Loss of range and competition with us is
what's harming most dwindling species.  Surely the same will hold true for
the insect world.

---------------
Richard Yarnell, SHAMBLES WORKSHOPS | No gimmick we try, no "scientific"
Beavercreek, OR. Makers of fine     | fix we attempt, will save our planet
Wooden Canoes, The Stack(R) urban   | until we reduce the population. Let's
composter, fly tying benches        | leave our kids a decent place to live.