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Annals of the Missouri Botanical Garden



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Twenty-seven bee taxa and 24 wasp taxa were collected on the open inflorescences and/or extra-floral nectaries of eight Acacia species in Victoria. Australia. Despite this superficial similarity in taxonomic diversity, bees outnumbered wasp foragers by 88% of the combined catch of winged Hymenoptera. Representatives from five families of bees were recorded , with the short-tongued Halictidae and Colletidae comprising the largest unit of native Apoidea on the Acacia species studied. Pollen foraging female bees of the genera Lasioglossum (Halictidae) and Leioproc1us (Colletidae ) comprised 83% of the combined catch of the two short-tongued families. The number of bee taxa collected on the Acacia species tended to increase from late winter through late autumn. Polylectic foraging bee taxa expanded from mid spring through late summer when the flowering of nectariferous Myrtaceae peaked. There was no correlation between the density and diversity of bees foraging on Acacia species bearing secreting extra-floral nectaries and those species that lacked extra -floral nectar while the inflorescences were blossoming. Representatives of seven families of wasps were collected on the eight Acacia species. No wasps, however, were collected on var. retinodes of A. retinodes. Approximately 66% of the wasps collected belonged to the families Sphecidae and Tiphiidae. Wasps repeatedly foraged on extra-floral nectar before foraging on nectarless inflorescences. The density and taxonomic diversity of wasps remained highest on the Acacia species that offered the greatest volume of sucrose-rich, extra-floral nectar (i.e., A. terminalis). Bees are probably more important pollinators of Acacia in southeastern Australia than are wasps. The direct influence of wasps on polyad dispersal appears to be nominal except in those Acacia species bearing functional extra-floral nectaries.

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