Uncovering the Floral Origins of Honey Bee Pollen in Colombian Tropical Dry Forest: A Low-Cost DNA Barcoding Approach Reveals Cactaceae Dominance

Abstract

Characterizing the botanical composition of pollen is essential to understanding the floral resources used by bees. While microscopy is the traditional method, it is time-consuming and limited in taxonomic resolution. Molecular tools such as DNA barcoding offer a more precise and cost-effective alternative for identifying plant taxa in mixed pollen samples. This study implemented a preliminary and cost-effective molecular approach to identify the botanical origin of pollen stored in bee bread from Apis mellifera hives in a tropical dry forest fragment in La Paz, Cesar, using rbcL and matK genes as markers. The chloroplast markers rbcL and matK were amplified and Sanger-sequenced from three independent bee hives, each processed in duplicate as technical replicates. The BLAST+ 2.17.0 results from Sanger sequences showed a sequence identity ranging from 89%–99%, with rbcL showing higher and more consistent matches than matK, suggesting stronger discriminatory power, while the lower identity in one hive indicated a more complex pollen mixture. However, matK detected a greater number of taxa overall (i.e., 70% of the total, 64 genera) compared with rbcL (i.e., 50%, 46 genera). Both markers overlapped in approximately 20% of the taxa, most of which (i.e., 94%) belonged to the family Cactaceae. This indicated that, although rbcL provided more reliable matches, matK contributed to broader taxonomic coverage, highlighting the complementarity of both markers for mixed pollen analyses. This approach highlights its value as an exploratory tool prior to applying high-throughput sequencing strategies. Furthermore, such studies may support the development of local honey brands by validating that their products originate mainly from the biodiversity of tropical dry forests, an ecosystem currently at risk, thereby conferring both ecological and market value.