Mark,
 
I do not understand why a subspecies should not exist in the same habitat, area,
locale, or whatever as the parent species.  The very finches you talk about on
the Galapagos exist side by side; species to subspecies.  Some interbreeding
goes on but for the most part each group selects within its own group.  Each
group tends to exploit a different niche within the environment.  So while they
may live side by side; they eat different seeds, nest in different areas, etc.
 
What do you think?
 
Tom Eichhorst in New Mexico, USA