Temporal and spatial variation of pollen content in pollen loads of Apis mellifera in the Yungas of northwest Argentina

The floral resources used by Apis mellifera as pollen source include those present in natural forests like the Yungas as well as forested areas. The aim of this work was to determine the main pollen resources harvested by A. mellifera and their variation during the honey production season. Forty pollen load samples were randomly collected from apiaries located in four sites (Tilquiza, El Fuerte, Los Alisos and Los Toldos) in spring and summer between 2011 and 2017. Sampling was conducted using pollen traps and the samples were subjected to conventional melissopalynological techniques. Pollen sources were identified using palynological atlases and compared with the reference palynotheca. A total of 70 pollen types distributed in 39 botanical families were identified, with the following families having the highest index of family importance (IF): Asteraceae (23.9), Fabaceae (19), Myrtaceae (12.8), Poaceae (8.3), Euphorbiaceae (8.2) and Vitaceae (4.3). The main resources used were: Mimosa, Eupatorium, Blepharocalyx salicifolius, Baccharis and Sebastiania. A pollen diagram was used to analyze the different pollen resources used throughout the study seasons. Species foraged in spring included B. salicifolius, Anadenanthera colubrina, Parapiptadenia excelsa and Sebastiania and those foraged in summer included Mimosa, Viguiera, Type Cissus and species of the family Poaceae; all of these species are native to the forest. The present results contribute to the knowledge of polliniferous species of the Yungas and evidence the importance of this bee as flower visitor in the forest.