The dissertation topic described by Allan Spessa is ambitious and
nicely designed, and should yield some very interesting data.  I raise three
points that you (Allan) might want to consider (no e-mail address, hence the
general posting).
 
1) You might want to collect some data to determine whether resources-
pollen (nectar?) - are limited under conditions of high Apis concentration.
This could be done by sampling flowers at the end of thier insect-attracting
phase and measuring pollen remaining in the flowers.  Measuring nectar
availability is more involved, but still possible.
 
2)  Will the availability of brood-sites affect your results?  If resources
aren't the major limiting factor, brood-sites might be.  I'm sure you've
already considered this, and will control accordingly.
 
3)  Finally, if your study sugests that competition is not a limiting factor
to Hylaeus populations, this doesn't preclude the possibility of past
competitive interactions.  In other words, the existing community of
colletid bees may be a "ghost of competition past".  The introduced Apis may
have eliminated some native species that were direct competitors, and the
existing populations may still exist because they had little niche overlap
with the Apis populations.  Any evidence for colletid extinctions since Apis
has been introduced?
 
Best of luck with the study, and keep us posted as your results come in.
 
					Gene Spears
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