Three species of native Thai honey bees exploit overlapping pollen resources: identification of bee flora from pollen loads and midguts from Apis cerana, A. dorsata and A. florea.
In this study, we investigated the bee flora utilised by the Thai honey bees, Apis cerana, A. dorsata and A. florea in Nan province, northern Thailand, through the identification of pollen grains from their pollen loads and midguts. We compared the pollen grains morphologically to match with local flowering plants and determined their protein concentration using a Bradford assay. The results showed that 8 families and 15 species were found by pollen load analysis whilst 12 families and 25 species were found from pollen grains of the bee midguts. The greatest number of bee flora was found from pollen loads of A. cerana, (11 species), while there were fewer for A. florea (10 species) and the fewest with A. dorsata (6 species). The highest number of bee flora species identified from pollen was found in the midgut of A. cerana, with 19 species, while A. florea had 13 and A. dorsata with only 11. The results show that the major pollen source plants of the three native honey bee species of Thailand were Mimosa pudica L., M. pigra, Celosia argentea L., Zea mays L., Wedelia trilobata L. and Syzygium malaccense L. The protein content ranged from 31.85±0.83 to 48.44±0.81 mg/100 mg pollen. The most abundant pollen source was from M. pudica L., perhaps because of the flower structure, shape, size, long blooming season, wide distribution, high protein concentration (43.31±0.79 mg/100 mg pollen) or a combination of these characteristics.