The current knowledge about pollinators in sub-Saharan Africa is extremely scarce. General pollinator distributions and resource usages are mainly unknown, as are the main pollinators of different crops (Timberlake and Morgan 2018). In early 2011, I travelled to an Afromontane area of Ethiopia, where arabica coffee, Coffea arabica L., has its origin, to survey coffee pollinators. I surveyed 19 coffee sites, most managed with organic practices, across a gradient from state-owned, shaded semi-plantation coffee to coffee grown sparsely, more or less wild, in the understory of disturbed natural forests (Fig 1a, b). I was surprised to find that native honey bees, Apis mellifera L., were the almost exclusive visitors. Out of 1226 collected potential coffee pollinator individuals, 1200 were bees, and 98% of these were honey bees (Samnegård et al. 2014). The dominance of honey bees in Ethiopian coffee pollination has also been found by Geeraert et al. (2019). Even though both studies found the proportion of alternative pollinators to increase in less disturbed forests (Samnegård et al. 2014, Geeraert et al. 2019), nonetheless honey bees dominated the pollinator assemblage in those areas and visiting rates of alternative pollinators were low. Like C. arabica, honey bees are native to Ethiopia (Fig 2a). In the introduced range of coffee, honey bees and other eusocial bees, i.e. bees that live together in perennial colonies, are the most frequent visitors (reviewed in Ngo et al. 2011), but solitary bees, i.e. bees that nest solitarily and have non-overlapping generations, also account for a significant proportion of visits in some systems. For example, in Indonesian coffee fields that varied in shade level and distances to forest, 44% of the visits to arabica coffee were made by 22 species of solitary bees, and the rest of the visits divided between seven different eusocial bee
species (Klein et al. 2003). In a study from sun-coffee sites in Brazil, where the honey bee was the most common visitor, 12 species of other eusocial bees (stingless bees from the tribe Meliponini) were present and accounted for 71% of the sampled bees (Saturni et al. 2016). These coffee systems seemed, according to the description in the papers, either similar (Indonesia, Klein et al. 2003) or more simplified (Brazil, Saturni et al. 2016), than the coffee systems I surveyed in Ethiopia. Since crops grown within their biogeographic region of origin in general are visited by a higher number of bee genera (Brown and Cunningham 2019), and the native Ethiopian coffee is grown in heterogeneous, organic systems, I found the total dominance of one visiting bee species very surprising.