We studied 24 colonies of Melipona, at the whole-colony level, by taking 34 pollen samples at 4 sites in the forested Yucatán Peninsular state of Quintana Roo. Samples were taken over a 20-year period. Our sampling involved removing pollen stored in each pot within the bee nest, acetolyzing the pollen, adding quantified Lycopodium spores to determine pollen species volume, and then identifying each pollen type to species using a light microscope, with our key and reference collection. Studies covered both the wet and dry season, 1996–2016. The bee population was analyzed considering (1) pollen-type frequency, (2) predominance, and (3) importance or volume. The last method, at the population level, identified significant pollen resource selection by the bee, with clear implications for conservation, management, and ecological study. Plants were ranked differently using the different methods, but the best method, using spores to quantify pollen volume, identified Fabaceae, Burseraceae, Myrtaceae, Solanaceae, and Bixaceae (formerly Cochlospermaceae) (32 total species or pollen types) as the most important resources, among 27 families, 47 genera, and 68 total species or pollen types. Three legumes, Gliricidia, Senna, and Lonchocarpus, were highly preferred, two of which provide nectar and pollen, and one (Senna) having only pollen. Further, each of the top families belongs to different plant orders; thus, bees were highly generalized in flower associations. They consistently use only certain forest trees and, occasionally, shrubs, and their competition with naturalized African honeybees, studied together at the same places, chiefly involves nectar and pollen of early successional woody species-Bursera and Eugenia. Other important pollen sources were Cochlospermum, Physalis, Gymnanthes, Myrcianthes, Thrinax, Chamaedorea, and Chrysophyllum.