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may avoid direct contact with each other. This may reduce the immediate effects of 
direct competition for the same energy source because foraging for the same nectar 
occurs at opposite ends of the same flowers. 
How interdependent, though, are Persoonia species, their true pollinators and their 
nectar/pollen thieves? Exoneura species have long been known to be polylectic foragers 
in Australia and we expected alien mixtures of pollens carried by Exoneura bees caught 
on Persoonia flowers based on the foraging record for this bee genus (Rayment 1935; 
Armstrong 1979; Bernhardt 1984, 1989). Some Exoneura species regularly visit both 
nectariferous taxa (Asteraceae, Myrtaceae, papilionoid legumes, Spyridium) and taxa 
that lack floral nectaries but produce copious pollen (Acacia, Dianella, Hihbertia) during 
the same foraging bout (Bernhardt 1989, 1995, and in progress). 
However, pollen load analysis in this study also shows that neither Cladocerapis nor 
Filiglossa bees always forage exclusively on Persoonia. Despite unusual morphological 
and ethological modifications that might be associated with foraging on Persoonia 
flowers (Maynard 1995), members of the two subgenera of Leioproctus take nectar 
and pollen from other plants. We must presume that mixed loads of pollen found in 
the scopae of such bees will still be used to feed larvae. 
Cladocerapis bees are dominant pollinators of Persoonia species at most study sites 
due, in part, to sheer numbers. Their mode of pollen collection is unlike any of the 
other prospective pollinators of Persoonia. However, there is still little direct evidence, 
at present, to indicate that Persoonia flowers and Cladocerapis bees are models of 
long-term co-adaptation. First, pollen load analyses of Cladocerapis bees indicate that 
Persoonia is not their exclusive source of pollen. Cladocerapis bees are facultative, not 
obligate, oligoleges (sensu Michener 1979) of Persoonia flowers. 
Second, taxonomists separate Exoneura from Leioproctus by family and the mouthparts of 
the two genera differ greatly in length. That is why sugar analyses of nectar of two 
Persoonia species seem so contradictory. Sucrose-dominant nectars like those of the two 
Persoonia species analysed are most often associated with long-tongue bees (Baker and 
Baker 1989) like members of the Apidae (e.g. Apis mellifera) and Anthophoridae (e.g. 
Exoneura). That may explain, in part, why naturalised A. mellifera forages so often on 
Persoonia. If the nectar of Persoonia flowers were hexose-dominant or hexose-rich then 
exclusive pollination by short-tongue bees might be expected (Kenrick et al. 1987; Baker 
and Baker 1989). While eastern Persoonia species and Cladocerapis bees certainly show 
some co-adapted features their interrelationship is not mutually exclusive. 
Of wider interest, note that the bees that forage preferentially on sympatric, co¬ 
blooming Persoonia species at Hilltop and Nerriga showed little evidence of resource 
partitioning. In his work on bee foraging in mediterranean habitats in the western 
Hemisphere Moldenke (1976) concluded that resource partitioning by bees showed 
a positive correlation with floral diversity. That is, as floral diversity increases over 
time, bees will visit the flowers of fewer plant species. Bees then avoid interspecific 
competition for the same pollen and/or nectar resources. 
Bernhardt (1989) did not find this correlation while studying the pollination ecology 
of Acacia species in south-eastern Australia. To the contrary, as floral diversity increased 
over the season, bees collected on Acacia species were more likely to carry the pollen 
of other co-blooming angiosperms. At the time, this was understood to be an exception 
to the rule, reflecting a narrow reward system since Acacia species in Australia lack 
floral nectaries. Since most bees that collect Acacia polyads are generalist foragers it 
was assumed that nectar from co-blooming taxa was essential to provide these bees 
with sufficient chemical energy to support continued foraging for pollen on nectarless 
Acacia. This should not have happened on Persoonia flowers at the Hilltop site. The 
flowers of each of the sympatric, Persoonia species sampled should have been dominated 
