Altitudinal partitioning of syrphid flies (Diptera) increases along elevation gradients in pollinator communities in the Eastern Himalayas, India

ABSTRACT The diversity and altitudinal distribution patterns of syrphid flies in the Neora Valley National Park, in the Eastern Himalaya was studied, including the ramifications of pollination by drone fly (Eristalis tenax) showing Batesian mimicry of honeybees. Considering the altitudinal variation and visitation rate, the study found a total of 30 Syrphidae species, among which Eristalis himalayensis, E. tenax, Chrysogaster sp., Episyrphus balteatus, Paragus haemorrhous and Syrphus dalhousiae had the highest encounter rate. The maximum number of species was observed at ≥ 2500 m asl. The diversity of Syrphidae in the Neora Valley reflects the supremacy of these flies over other pollinator insects in the study area. The mean visit per hour of drone fly (E. tenax) was 21 ± 2.73SE (SE – standard error) individual at the lower altitudes but the rate was higher (37.1 ± 4.09SE) in the absence of honeybees at the higher altitudes. More information about the primary determinants of the dynamic nature of pollination is required in this area in order to understand plant–pollinator responses to global warming.