African endemic stingless bees as an efficient alternative pollinator to honey bees in greenhouse cucumber (<i>Cucumis sativus</i> L)

The current honey bee decline necessitates the use of alternative native pollinators to ensure global food security. Here, we compared the pollination behaviour and efficiency of the African honey bee (<i>Apis mellifera</i>) and six African endemic Meliponini (<i>Meliponula bocandei, Dactylurina schmidti, Meliponula lendliana, Hypotrigona gribodoi, Meliponula ferruginea</i> and <i>Meliponula togoensis</i>) in a greenhouse with the non-parthenocarpic cucumber variety <i>Super Marketer</i>. Honey bees and <i>D. schmidti</i> started foraging on introduction in the greenhouse, while <i>M. lendliana</i> and <i>M. togoensis</i> showed the longest delay. In most species, foragers collected nectar and pollen, excepting <i>M. bocandei</i> that specialized in nectar collection, and <i>H. gribodoi</i> and <i>M. togoensis,</i> specialized in pollen collection. African honey bees visited flowers the shortest, while <i>H. gribodoi</i> and <i>D. schmidti</i> had a 2-fold probing time, on average. Most stingless bees species had a lower hive activity with fewer foragers encountered per hour than for honey bees, except <i>D. schmidti</i>. <i>M. bocandei, M. ferruginea</i>, <i>A. mellifera scutellata</i> and <i>H. gribodoi,</i> yielded a seed germination percentage of around 90%. <i>M. lendliana</i>, <i>M. togoensis</i> and <i>D. schmidti</i> yielded a much lower seed germination percentage around 30%, which indicates that the quality of pollination was remarkably lower by using these three species. The highest sugar content was recorded in fruits from flowers pollinated by <i>M. bocandei,</i> African honey bees<i>, D. schimdti</i> or <i>M. togoensis</i> with the same solid content as the gold standard method, i.e., hand cross-pollination. We found that <i>M. bocandei</i> was the most efficient cucumber pollinator of all species tested: because pollination by this species yielded the largest and heaviest fruits and the highest seed numbers.