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Several studies have shown that nectar-inhabiting bacteria and fungi influence plant and pollinator fitness by modulating their mutualistic interactions. However, little is known about the nectar microbe communities in African agricultural crops, and how visitations by different Afrotropical bee species shape floral nectar microbial community, chemistry, and plant reproductive fitness. In this study, we explored these interactions focusing on Afrotropical pollinator bee species found in Kenya. We found that the stingless bee species Hypotrigona gribodoi and Dactylurina schmidti, and the African savannah honey bee Apis mellifera scutellata introduce only bacteria into the floral nectar of the yellow bell pepper plant Capsicum annum cultivated in a greenhouse, which differed in their volatile emission profiles. Additionally, nectar probing by these bee species shaped the microbiome of C. annum, and significantly affected nectar volume and sugar composition. These findings lay the foundation for further exploration of the microbial influence into plant-pollinator interactions in this country.

An increasing demand for pollination services highlights the need for research on alternative pollinators for greenhouse and open field food crops. We compared the foraging behaviour and effectiveness of seven endemic African Meliponinae (Meliponula bocandei, Dactylurina schmidti, Plebeina hildebrandti, Meliponula lendliana, Hypotrigona gribodoi, Meliponula ferruginea, Meliponula togoensis) as alternative pollinators to honey bees of greenhouse cultivated Cantaloupe melons. It was observed that honey bees started foraging sooner after introduction in the greenhouse (av. 4 days) than the stingless bee species (8 to 16 days). Stingless bees were mainly harvesting nectar (ca. 2/3 of all flower visits) and M. ferruginea, M. togoensis, H. gribodoi and P. hildebrandti spent more time collecting nectar than other stingless bee species. Fruit maturation was significantly faster when flowers were pollinated by stingless bees compared to honey bees, with the shortest fruit maturation time found when flowers were pollinated by M. bocandei and H. gribodoi. All treatments resulted in fruits of similar roundness and ellipsoid ratios. The highest fruit weight and fruit volume were obtained from flowers pollinated by either manual pollination, H. gribodoi, M. bocandei, M. lendliana and P. hildebrandti compared to honey bees. Correspondingly, pollination by the latter 5 species resulted in the highest seed counts per fruit, although these differences did not affect seed weight or volume. Altogether, our results indicate that stingless bees such as H. gribodoi, M. bocandei, M. lendliana and P. hildebrandti are more efficient pollinators of sweet melon than A. m. scutellata and can be recommended for use in greenhouse crops.

Stingless bees (Apidae: Meliponini) provide pollination services to crops and produce high–quality honey. The application of agrochemicals during the management of crop pests is an increasing threat to pollinators and the ecosystem services they provide. Biopesticides are considered as better alternatives; however, there is limited evidence of their impact on stingless bees. We evaluated the effect of the most widely used African fungal biopesticide (Metarhizium anisopliaeICIPE 69) on mortality, foraging behavior and pollination success of the African stingless beeMeliponula ferrugineaunder semi-field conditions. Colonies ofM. ferrugineawere introduced into four 24 m2greenhouse compartments containing blooming cucumber (Cucumis sativus) plants. Cucumber plants were sprayed with a suspension of the biopesticide alongside a sterile 0.05% Triton–100–X (control). The experiment was repeated three times during different cucumber growing seasons. Biopesticide application did not significantly affectM. ferrugineamortality, flight activity, flower visitation, pollen foraging,C. sativusfruit set orC. sativusyield. Forager bees acquired a high number of conidia (7,600 ± 54 conidia /bee) immediately after biopesticide application; however, a significant decline was observed in the subsequent days. Conidial persistence and viability on plant surfaces declined significantly with days. There was no correlation between conidial acquisition and pollen load by forager bees (657 ± 29 pollen/bee). This study demonstrates thatM. anisopliaeICIPE 69 did not negatively impactM. ferrugineamortality, pollination behaviour and success, and can therefore be safely used in stingless bee–dependent crop systems.

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 (Apis mellifera) and six African endemic Meliponini (Meliponula bocandei, Dactylurina schmidti, Meliponula lendliana, Hypotrigona gribodoi, Meliponula ferruginea and Meliponula togoensis) in a greenhouse with the non-parthenocarpic cucumber variety Super Marketer. Honey bees and D. schmidti started foraging on introduction in the greenhouse, while M. lendliana and M. togoensis showed the longest delay. In most species, foragers collected nectar and pollen, excepting M. bocandei that specialized in nectar collection, and H. gribodoi and M. togoensis, specialized in pollen collection. African honey bees visited flowers the shortest, while H. gribodoi and D. schmidti 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 D. schmidti. M. bocandei, M. ferruginea, A. mellifera scutellata and H. gribodoi, yielded a seed germination percentage of around 90%. M. lendliana, M. togoensis and D. schmidti 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 M. bocandei, African honey bees, D. schimdti or M. togoensis with the same solid content as the gold standard method, i.e., hand cross-pollination. We found that M. bocandei 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.

Pollinators are of essential importance for sustainable agriculture. However, pollination efficiency depends on interacting factors such as pollinator behaviour and morphology. We compared the effect of probing time length and visit frequency of two distinct body size African stingless bee species (Meliponula bocandei, Dactylurina schmidti) as alternative pollinators to Apis mellifera scutellata on greenhouse cultivated cucumber. We found differences in morphometric characteristics, between a set of 9 body parameters. Bee body size was the morphological feature that varied the most among bee species. On average, body size was largest in honeybees, followed by M. bocandei, and finally D. schmidti, which was the smallest. Glossa length was different between the bee species: A. mellifera scutellata (2.86 ± 0.026 mm), M. bocandei (2.20 ± 0.031 mm), D. schmidti (0.72 ± 0.025 mm). Such differences among bee species in body parameters correspondingly affected nectar probing times during a single flower visit, which were different for the bee species. D. schmidti (3.34 ± 0.56 s) had the longest probing time, while M. bocandei (2.57 s) had the shortest. Fruit quality was strongly positively influenced by the visit duration during a single visit on female flowers. The slope of fruit quality produced was higher in flowers pollinated by M. bocandei. During a single flower visit, heavier and bigger fruits were obtained in the gold standard hand cross pollination and flowers pollinated by M. bocandei. The bee species and the number of visits significantly impacted fruit weight, fruit volume and number of seeds. Subsequent visit performed by M. bocandei positively impacted fruit quality. Three visits on a flower were enough to ensure the production of high-quality fruits. Fruit sweetness depended on the number of visits received by the flower, but not on the bee species that performed the visit. Altogether, our results indicate that the stingless bees M. bocandei is more an efficient pollinator of cucumber than A. m. scutellata and D. schmidti and can be recommended for use under greenhouse cultivation.

This study assessed the nontarget effect of entomopathogenic fungi on the Western honey bee Apis mellifera L. and the African stingless bee Meliponula ferruginea Cockrell (Hymenoptera: Apidae). Pathogenicity of five Metarhizium anisopliae (ICIPE 7, ICIPE 20, ICIPE 62, ICIPE 69, and ICIPE 78) (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae) and one of Beauveria bassiana (ICIPE 284) (Balsamo) Vuillemin (Hypocreales: Cordicipitaceae) isolates were evaluated on bees at 108 conidia/ml. Conidial acquisition was evaluated immediately after exposure. Apis mellifera acquired more conidia (2.8 × 104–1.3 × 105 conidia per bee) compared to M. ferruginea (1.1 × 104–2.3 × 104 conidia per bee). In the bioassay with A. mellifera, ICIPE 7, ICIPE 20, and ICIPE 69 moderately reduced the survival by 16.9, 17.4, 15.3%, with lethal times LT10 = 7.4, 7.6, 8.1 d and LT25 = 8.7, 10.0, 9.9 d, respectively. The three isolates caused A. mellifera mycosis of 11.6–18.5%. None of the isolates had a significant effect on M. ferruginea. The tested isolates are nontoxic to bees according to the International Organization of Biological Control (IOBC) classification. However, the effect of ICIPE 7, ICIPE 20, and ICIPE 69 merits further studies on bee colonies, especially those of A. mellifera, under field conditions.

The European Union (EU) (Grant Contract No. DCI-FOOD/2013/313-659: African Reference Laboratory (with satellite stations) for the Management of Pollination Bee Diseases and Pests for Food Security); the South African National Research Foundation (NRF) Research Career Advancement Fellowship (Grant no: 91419) to AAY; NRF Incentive Funding for Rated Researchers to CWWP and AAY; UK Aid from the UK Government; Swedish International Development Cooperation Agency (Sida); the Swiss Agency for Development and Cooperation (SDC) and the Kenyan Government. The first author was supported by a German Academic Exchange Service (DAAD) In-Region Postgraduate Scholarship.

Stingless bees are important pollinators of wild plants and crops. The identity of stingless bee species in Africa has not been fully documented. The present study explored the utility of morphometrics and DNA barcoding for identification of African stingless bee populations, and to further employ these tools to identify potential cryptic variation within species. Stingless bee samples were collected from three ecological zones, namely Kakamega Forest, Mwingi and Arabuko-Sokoke Forest, which are geographically distant and cover high, medium and low altitudes, respectively. Forewing and hind leg morphometric characters were measured to determine the extent of morphological variation between the populations. DNA barcodes were generated from the mitochondrial cytochrome c-oxidase I (COI) gene. Principal Component Analysis (PCA) on the morphometric measurements separated the bee samples into three clusters: (1) Meliponula bocandei; (2) Meliponula lendliana + Plebeina hildebrandti; (3) Dactylurina schmidti + Meliponula ferruginea black + Meliponula ferruginea reddish brown, but Canonical Variate Analysis (CVA) separated all the species except the two morphospecies (M. ferruginea reddish brown and black). The analysis of the COI sequences showed that DNA barcoding can be used to identify all the species studied and revealed remarkable genetic distance (7.3%) between the two M. ferruginea morphs. This is the first genetic evidence that M. ferruginea black and M. ferruginea reddish brown are separate species.

A study was carried out in Kakamega forest, in the western region of Kenya, to evaluate the effectiveness of the stingless bee Hypotrigona gribodoi (Magretti, 1884) on the pollination of green pepper. Three treatments were applied and consisted of self-pollination, pollination by feral pollinators in the open field and pollination by H. gribodoi in a net cage. The differences in fruit yield and seed quality were compared among treatments. Flowers pollinated by H. gribodoi produced the heaviest fruits with the highest seed numbers followed by feral pollinators and lastly self-pollinated flowers. Moreover, seeds were significantly bigger in size in fruits resulting from flowers pollinated by H. gribodoi compared to fruits obtained from self-pollinated flowers or flowers pollinated by feral insects. We, therefore, conclude that H. gribodoi is an efficient pollinator of green pepper in the tropical region of East Africa.

Natural habitat degradation often involves the reduction or disappearance of bee species. In Africa, stingless bees are hunted for honey, which is used as food, for medicinal purposes, and for traditional rituals. Severe habitat degradation due to human settlement is hypothesized to have a negative impact on the species diversity of the African stingless bee species. In this paper, we assess the impact of habitat degradation on the diversity of five stingless bee species across different habitats in the tropical rainforest of Kenya (indigenous forest, mixed indigenous forest) and its neighbouring landscape (grassland, village) in western Kenya. The species fauna, nest occurrence, and species diversity of the stingless bee species varied across the different habitats. The number of nesting habitats of the meliponine species varied between habitats in the tropical rainforest.Meliponula ferruginea(reddish brown) nested in five habitats, whileMeliponula bocandeiandMeliponula ferruginea(black) nested only in two habitat types. The species richness decreased within the different types of habitats and the indigenous and mixed indigenous forest contained more species than other habitats. The fauna composition in both homesteads was exclusively similar, while the indigenous and mixed indigenous forests were mostly similar. Similarity in habitat preferences for nesting was revealed betweenM. bocandeivsPlebeina hildebrandtiandM. ferruginea(reddish brown) vsHypotrigona gribodoi. The natural native indigenous forest had the most diverse community compared to the degraded habitats. There are taxon-specific responses to habitat change; and in our study, there is clear value in conserving the native indigenous forest.

Previous studies have shown that natural honeybee and bumble bee colonies are hosts of the small hive beetle (SHB) Aethina tumida, a pest of honeybee colonies in various regions of the world. Recent studies also reported the presence of SHBs in colonies of certain meliponine bee species. In this study, we investigated whether SHBs detect odors of African meliponine bees and their hive matrix components. We also compared the chemical profiles of the honeybee Apis mellifera scutellata and meliponine bee odors in order to identify common potential semiochemicals between the two bee species. We used dual-choice olfactometric assays to test the responses of adult male and female SHBs to intact colony odors from six meliponine bee species, namely Hypotrigona gribodoi, Meliponula ferruginea (black), M. ferruginea (reddish-brown), Plebeina hildbrandti, M. bocandei and M. lendiliana and their hive matrix components including pot honey, pot pollen, cerumen (involucrum) and propolis (batumen). We found that female SHBs responded more strongly to odors from intact colonies, pot honey and pollen from five out of the six species tested than male beetles. Chemical analysis identified several common components in colony odors emitted by both honeybees and a representative meliponine bee species, M. ferruginea (black). In particular, nine of these common components previously have been shown in honeybee volatiles to be semiochemicals for the SHB, suggesting that African meliponine bees can also serve as potential alternate hosts for the beetle. The implications of these results are discussed in the context of domesticating African meliponine bees in man-made hives for the pollination of crops.