Botanical Origin of Pollen Collected by Apis mellifera scutellata Lepeletier (Hymenoptera: Apidae) in a Suburb of Pretoria, South Africa

Abstract

The savannah honeybee, Apis mellifera scutellata Lepeletier (Hymenoptera: Apidae), is a eusocial insect that forages for nectar and pollen on a variety of flowering plants. However, it is selective of plants from which it forages. The preferred species are called bee-plants. The concept of bee-plants recognises that flowers do not have the same pollen and nectar value to honeybees. Thus, the strength of honeybee colonies is dependent on the presence of bee-plants throughout the year at any given locality. A study was conducted during March 2013–February 2015 to establish the presence of bee-plants and their phenology within 2 km radius of the apiary at ARC-Plant Protection Research Institute's farm in Rietondale, a suburb of Pretoria. A total of 247 flowering plant species from 70 families, comprising indigenous and exotic trees, shrubs and grasses, was recorded during March 2013–February 2014. Most plant species flowered during April, a smaller proportion during February and October, and only a few during June. Flowers of each plant species were sampled in order to make reference pollen grain slides. To determine bee-plants, a pollen trap was fitted to the entrance of one of five Langstroth hives on a fortnightly rotation during March 2014–February 2015 in order to intercept pollen pellets from the hind legs of returning foragers. A total of 2403 pollen pellets were recovered, most of which (1263) were collected during April and none during October. At the laboratory, about a quarter of each pellet was dissolved in distilled water and pollen grain slides were prepared. These slides were matched against reference pollen grain slides using a compound microscope. It was established that honeybees foraged from only 30 plant species. During summer (December–February), pollen was collected mostly from Persicaria capitata (Polygonaceae), Tithonia rotundifolia (Asteraceae) during autumn (March-May), Acacia galpinnii (Fabaceae) during winter (June–August), and Ageratum conyzoides (Asteraceae) during spring (September–November). These results show that honeybees had access to pollen sources that were sufficient to sustain their colonies throughout the year. As bee-plants were continuously available in the vicinity of the Rietondale farm, this site could be ideal for urban beekeeping.