Ongoing expansion of large-scale agriculture critically threatens natural habitats and the pollination services they offer. The objective of this study was to examine and understand how local and landscape drivers affect bee functional groups and ecological traits across study sites of different environmental gradients in central Uganda. Bee functional groups responses were predicted by various predictors operating at different scales. The patterns of wild and cultivated plant diversity, nesting resource availability, % cover of semi-natural habitats, and presence of forests/wetlands in the vicinity of fields were found to be key determinants of occurrence and activities of different bee functional groups in mosaic farm-landscape of Uganda (P<0.05). Compared to the abundance, the species richness of different bee functional groups was predicted by a different set of environmental and landscape factors. The abundance and species richness of most bee functional groups examined were positively related (P<0.05) to the % cover of semi-natural habitats and negatively related to both the cultivation intensity and forest distance. The abundance and species richness of most functional groups were more related positively (P<0.05) to the species richness and density of wild blooming plants than to the abundance of pollinator-dependent crops and non-pollinator dependent crops. The abundance and species richness of tiny, small-bodied, solitary, ground-nesting, olilectic, long-tongued, univoltine and bivoltine bees were found to be more threatened by cultivation intensity and forest distance and related environmental disrupting factors (e.g. climate change). Thus, bee populations belonging to these bee groups may be particularly affected by habitat degradation. Such situation is likely leading to low yield for crops that require species-visits from these bee groups to achieve high pollination success. Consequently, landscape and habitat management to conserve a diversity of bee functional groups nearby fields should aim at increasing the proportion cover of natural and semi-natural habitats in the farm-landscape, slow the intensity of animal/crop production, as well as recommend farmers to adopt pollinator-friendly farming practices (eg. avoid pesticide sprays, promote on farm tree cover, apply good weeding regimes, etc).
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