The short term impact of a collection of commercial Cape honeybee (Apis mellifera capensis Esch.) colonies on invertebrate flower visitors within a near pristine fynbos habitat in the Cape Floristic Region

Brand, Mariette Rieks (2009-03)

Thesis (MScConsEcol (Conservation Ecology and Entomology)--University of Stellenbosch, 2009.


Apiculture in the Western Cape is a well-developed industry based on honey production and pollination services to agriculture. Apart from Eucalyptus trees, fynbos vegetation serves well as bee forage to managed honeybee colonies outside the agricultural pollination season. Eucalyptus trees are cleared as invasive plant species while fynbos are rigorously protected as one of the 34 Biodiversity Hotspots identified worldwide. Thus, bee forage is in short supply and is most probably the only limitation to the number of honeybee colonies that beekeepers can feasibly maintain. The impact of a collection of commercially managed honeybee colonies on other floral resource-dependent species in the Cape Floristic Region is unknown. This is one of the first studies on the topic in South Africa and specifically in the Western Cape. Managed hives were introduced to near pristine fynbos habitat in De Hoop Nature Reserve and Marine Protected Area during July. The aim was to induce stronger competition for floral resources through greater resource exploitation by managed honeybee colonies and record the change in foraging behaviour for several insect guilds on specific plant species. The results suggest that eight hives per site proved insufficient to increase honeybee density above the natural density of honeybees. Honeybee abundance did not increase during the presence of the managed hives, while honeybee visitation frequency was significantly greater during the presence of the managed hives. Neither the abundance nor the visitation frequency of non-Apis bees and wasps differed significantly between treatments. Honeybees were the most abundant foragers on the three focal plant species during all three treatments and also made the most visits to flowers. Honeybee abundance and visitation frequency increased with distance from the managed hives. The significant increase in honeybee visitation frequency during hive presence, coupled with a significant decrease in the time honeybees spent per flower extracting nectar, were an indication of a lower standing crop of nectar during that treatment. Nevertheless, no competition for floral resources was obvious, as the number of honeybees did not increase the abundance and visitation frequency of all other insect guilds (except for a significant decrease in Muscidae, which could be ascribed to changes in weather conditions).

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