Patterns of bee diversity in mosaic agricultural landscapes of central Uganda: implication of pollination services conservation for food security

Little is known about bee communities and pollination services conservation strategies in sub-Sahara Africa. A study was conducted at 26 different sites with varying local landscape characteristics in farmlands of central Uganda in 2006. Bees were sampled using coloured pantraps, handnet and line transect counts. Overall 80,883 bee individuals from 6 families and 652 species were encountered. The bee fauna was characterized by a lower diversity of Melittidae and Andrenidae and a high diversity of Apidae, Megachilidae and Halictidae. Megachile and Lasioglossum were the two most species-rich genera. The most abundant species was Apis mellifera adansonii Linnaeus (23 % of total individuals) followed by Hypotrigona gribodoi Magretti (19 %), Meliponula ferruginea Lepeletier (13 %), Lasioglossum ugandicum Cockerell (7 %), Apis mellifera scutellata Latreille (6 %), Allodapula acutigera Cockerell (6 %), Ceratina rufigastra Cockerell (5 %), Ceratina tanganyicensis Strand (5 %), Braunsapis angolensis Cockerell (5 %), Megachile rufipes Fabricius (5 %), Meliponula bocandei Spinola (5 %) and Seladonia jucundus Smith (5 %). The mean number of species recorded per study site per day ranged between 14 and 49, whereas the abundance ranged between 188 and 1,859 individuals. Study sites in areas with intense land-use had species-poor bee communities compared to sites with medium to low land-use intensities. Study sites with riparian forest fragments and wetlands, or with forest fallows in their vicinity had significantly (P < 0.05) higher species richness and diversity than sites dominated by small-scale monoculture/polyculture fields or sites dominated by either simple or complex traditional agroforestry systems. An ordination analysis also revealed that bee communities were significantly (P < 0.01) influenced by the presence of semi-natural habitats (woodlands, fallows) and forest fragments in the surrounding of fields. Thus, natural and semi-natural habitats are of great value for afrotropical farmland bee communities. There is a need to put in place strategies and policies for semi-natural and forest fragments preservation for spatio-temporal stability of pollination services in rural landscapes. Farmers are recommended to increase on-farm trees cover to safeguard and enhance pollination function and services in fields. Mimicking natural vegetation through promoting establishment of forest plantations and village community forestry in rural landscapes is also critical for conserving pollination services.