Spatio-temporal pollen foraging dynamics of Western honey bee during litchi bloom revealed through DNA barcoding

Introduction Understanding the spatio-temporal dynamics of pollen foraging by Apis mellifera is essential for optimizing pollination services and sustainable apiary management in litchi ( Litchi chinensis ) orchards. This study investigated pollen foraging patterns across major litchi-growing areas of Muzaffarpur District, Bihar, India, during the peak flowering period. Methods The study was conducted in 11 litchi orchards from 14 th March–6 th April 2025. Wooden pollen traps were installed on five healthy honeybee colonies per orchard and operated for 7 h per day (09:00–16:00 h) at 6-day intervals. Pollen pellets were sorted, weighed, and identified using DNA barcoding, with sequence validation against GenBank and BOLD databases followed by phylogenetic analysis. A factorial randomized block design was used to evaluate the effects of orchard location (11 orchards), sampling week (4 weeks), and pollen species (11 taxa) on pollen quantity and percentage. Results DNA barcoding confirmed the presence of 11 plant species in the bee-collected pollen spectrum, and all sequences were deposited in GenBank. Significant effects of orchard location, sampling week, pollen species, and all two- and three-way interactions were observed for both pollen quantity and pollen percentage ( p < 0.01). Litchi chinensis was the predominant pollen source across most orchards, with maximum abundance during Weeks 2–3, corresponding to peak anthesis. Secondary pollen sources, including Bombax ceiba, Pithecellobium dulce, Coriandrum sativum , contributed variably across locations and sampling periods. The highest quantities of litchi pollen were recorded at Manika Ghazi, Sahila, and Prahaladpur, whereas lower pollen availability was observed in several orchards during the early flowering stage. Discussion The findings demonstrate pronounced spatial and temporal variation in floral resource utilization by A. mellifera during litchi bloom and confirm the effectiveness of DNA barcoding for accurate pollen source identification. Honeybee foraging was strongly dominated by litchi pollen during peak flowering but diversified according to local floral composition and flowering phenology. These results provide practical guidance for strategic apiary placement, pollination management, refinement of regional floral calendars, and conservation of complementary floral resources to sustain honeybee nutrition and enhance litchi productivity.