The botanical origin of cerumen and propolis of Indian stingless bees (Tetragonula iridipennis Smith): pollen spectrum does not accurately indicate latex and resin sources

Abstract

Stingless bees collect plant latex and resin to produce cerumen and propolis. Cerumen is primarily used for nest construction, such as brood cells, storage pots, and involucrum. Propolis is mainly used as a sealing material and for predator and pathogen defense. Knowledge about the botanical origin of these materials is vital for sustainable bee management. We performed (i) direct observation method by field surveys and (ii) indirect assumption method via pollen analysis of corbicular and in-hive stored latex/resin, cerumen, and propolis of Tetragonula iridipennis. By the direct observation method, we identified 25 plant species as latex/resin sources of the stingless bees; frequently encountered were Artocarpus heterophyllus, Calotropis gigantea, Ficus benghalensis, Ficus religiosa, Mangifera indica, Tabernaemontana divaricata, and Vachellia nilotica. From pollen analyses, we found diverse pollen types, including pollens of polleniferous plants. Comparatively higher pollen content was found in cerumen and propolis samples than in the in-hive stored latex/resin and corbicular latex/resin loads. But all the pollen types do not indicate actual latex/resin sources for the bee species. These pollen types came from the foraging environment and additionally during the transport of latex/resin within the hive and the processing of latex/resin into cerumen and propolis. Therefore, we can conclude that the pollen content of corbicular and in-hive stored latex/resin, cerumen, and propolis is not truly inferring its botanical origin; it requires alternative techniques like the direct observation method or chemical profiling.