Regional variation in morphometric traits of drone honey bees (Apis mellifera L.): A comparative study between Punjab and Himachal Pradesh, India

Present study aimed to investigate the phenotypic diversification of A. mellifera drones in response to altitudinal and climatic differences across the northern region of India. Drone samples were collected from two distinct geographical locations: the Himalayan Honey Bee Farm in Kangra, Himachal Pradesh (a highaltitude site), and the Tiwana Bee Farm in Ludhiana, Punjab (a lowland agricultural region). Morphometric characterization was performed on 20 anatomical traits using a calibrated image acquisition zoom-stereo microscope. Specimens were preserved in 70% ethanol and dissected for precise measurement of body segments. Morphological analysis revealed that individuals from Kangra consistently exhibited larger dimensions across several key traits, including total body length (15.2 ± 0.12 mm vs. 14.5 ± 0.18 mm), hind wing length (7.37 ± 0.19 mm vs. 6.34 ± 0.18 mm), and abdomen length (6.86 ± 0.09 mm vs. 6.43 ± 0.19 mm), compared to their Ludhiana counterparts. These inter-population differences suggest environmentally induced phenotypic plasticity, potentially influenced by variations in altitude, temperature, and floral resource availability. The findings underscore the utility of morphometric analyses as a non-invasive tool to detect ecological adaptation and population structuring in honey bees and contributes valuable insight into the influence of environmental pressures on bee morphology.