User Import module assigns role that I did not select

The User Import module works well for me except in one particular case when I specify that a role called "DDS applicant" should be assigned during import the result is that "DDS applicant" and "PharmD applicant" and "authenticated user" are assigned. I only want "DDS applicant" and "authenticated user" assigned. The problem is consistently reproducible. If I import a CSV and specify only "PharmD applicant" to be assigned, only "PharmD applicant" is assigned -- it works as I expect. What might cause User Import to assign a role that was not selected during import in this manner? I think I might be missing something obvious, but I can't figure out what. Thanks!