Pollen composition in the corbicula reflects the foraging activity of sympatric honey bees and stingless bees in Indonesia

Abstract

The corbicula or pollen basket plays a central role in pollen collection in honey bees and stingless bees, thus can be applied to study floral resource use by foraging bees. We investigated corbicular pollen load composition and foraging activity of sympatric honey bees (Apis cerana) and stingless bees (Geniotrigona thoracica and Heterotrigona itama) in a beekeeping area in North Sumatra, Indonesia. A total of 44 corbicular pollen loads were collected from three bee species (two colonies per species). Pollen samples were processed using the acetolysis method and identified based on morphology. Pollen types were quantified by relative abundance and differences among species were evaluated using diversity indices and multivariate analyses based on Bray–Curtis dissimilarity. Vegetation surveys were conducted to assess floral resource availability and their relationship with pollen composition. Foraging activity was observed over three consecutive days and analyzed in relation to environmental factors, with temporal overlap assessed using overlap indices. Pollen composition differed among species, with stingless bees showing higher pollen diversity than A. cerana, particularly in H. itama compared to G. thoracica. Multivariate analyses revealed significant but weakly separated pollen composition, indicating partial overlap in pollen use among the three bee species, with Cocos nucifera as a shared key floral resource. Despite the availability of flowering plants, pollen composition reflected selective rather than proportional use of available floral resources. Differences in pollen composition were associated with distinct pollen-foraging timing influenced by environmental factors. Apis cerana exhibited higher pollen-collecting activity in the morning and declined toward midday, whereas stingless bees maintained relatively consistent activity throughout the day. Temporal overlap analysis indicated partial separation in foraging activity, suggesting temporal resource partitioning between honey bees and stingless bees. These findings highlight the importance of maintaining diverse and continuous floral resources to support coexistence in sympatric managed bee communities.

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