Dear Dr. Liz Day,
I don't know what exactly you mean by "same geographic region", nor what
would you consider as "actual research", but Dr. J.R.Cure and I have a
paper in press in the 'Studies on Neotropical Fauna and Environment' (it
may be already published) that may have some data of interest for you.
The paper does not deal with swamps and prairies, however. It is a
comparison between bee fauna in areas bellow 1000 meters altitude and
areas above 1400 meters above sea level, in a specific region of Brazil.
We have some comments on the replacement of one species of Bombus by
another one in the higher areas.
   Best wishes,
                Fernando A. Silveira
                Snow Entomological Museum
                The University of Kansas
                e-mail [log in to unmask]