Dear List People,
 
The question of resource competition between honeybees and native bees has
been a rather hot potato in Australia for a couple of years, with the most
recent work by Pyke and Balzar (1982), and Sugden and Pyke (1991).
Currently, several states are in the process of restricting bee-keeper
access to National Parks, mainly through non-renewel of site licenses.
However, several aspects (mainly experimental design) of the previously
published work has been criticised, and the situation re competition is not
yet clear.   Beekeepers in Australia are very organized and are lobbying
the land-management groups effectively (although they are also funding
basic research into resource competition between honeybees and native
nectarivorous and pollenivorus fauna).   Since honey constitutes a
reasonably large export item for Australia, the issue of curtailing
bee-keeper access in these times of recession is rather thorny!
 
We have been funded by WWF to look at resource competition between
honeybees and native allodapine bees.   One allodapine, Exoneura bicolor,
is particularly suitable (in at least some respects) because we can move
nests from area to area (with minimal adult mortality) and therefore we can
set up our 'test bees' in control and experimental sites utlizing a
homogeneous source population.   We have carried out 3 experiments based on
non-simulated and typical beekeeper practices (approx. 120 hives per site
over a period of approx. 10 weeks during eucalyptus honey-flow conditions),
and 8 experiments looking at 'feral honeybee density' conditions (feral
populations were augmented by 6 hives per experimental site, since it is
impossible to locate and remove all existing feral hives).    In both
experimental types, native bees are moved into an area, left for 2 - 6
months and then analysed.  Periods of placement and termination are set to
avoid confounding effects of dispersal after brood maturity, and to look
for effects that may be specific to particular colony development periods.
 We have utilized 4 experimental and 4 control sites, with approx. 80-100
Exoneura nests per site per experiment.   We have looked at colony
survival, colony size, brood number and brood developmental rates, as well
as secondary occupation by other alodapines,  non-Exoneura insects, etc.
 
Surprisingly, we have found NO evidence at all that honeybees depress brood
rearing efficiency (either brood number, age, dry weight, etc.).   Pollen
analyses show that there is a very large (probably complete) overlap in
pollen utilization, so we would expect to find evidence of competition if
it occurs.   However, we have found in nearly all experiments that colony
survival of Exoneura is significantly higher in experimental sites.   We
suspect that this may be due to predator satiation by Apis.    We are
currently trying to address the possibility that predator satiation in one
season may lead to enhanced predator presence in following seasons (when
honeybees  have been moved away and floral resources may be more limiting)
 
We have a couple of manuscripts in prep, but would welcome any
ideas/responses from others at this point.
 
I have a new PhD student, Allan Spessa, who is beginning a similar study,
but using short-tongued Hylaeus bees.    Since Exoneura is highly
polylectic, results based on it may not be applicable to the colletids,
which form the dominant family in the bee fauna of Australia and are often
restricted to the Myrtacea.   Allan will write further to outline his
approach.
 
We would be most interested to hear from any others who have recently
addressed these problems, and particularly whether evidence for predator
satiation has been found.
 
Michael Schwarz
(La Trobe Univ. Australia)
 
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Dr Michael Schwarz
Zoology Dept
La Trobe University
Ph +61 3 479-2201
Fax +61 3 479-1188
Internet [log in to unmask]
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