Seasonal gut microbiota dynamics and colony performance under stationary and short-distance migratory beekeeping in Apis mellifera ligustica

Abstract

Honey bee gut microbiota play important roles in host nutrition, immune regulation, and health, and their composition can vary in response to environmental conditions, diet, seasonality, and beekeeping management. In this two-year field study, we investigated seasonal variation in the gut bacterial communities of Apis mellifera ligustica colonies maintained under stationary or short-distance migratory beekeeping management. Six colonies originating from the same experimental apiary were assigned to stationary or migratory management, with three migratory colonies seasonally transferred to Mount Taburno during summer and three stationary colonies remaining at Castelpoto. Bacterial communities were characterized by high-throughput sequencing of the V1–V3 region of the 16S rRNA gene. The gut microbiota was consistently dominated by characteristic honey bee-associated taxa, particularly Gilliamella and Snodgrassella , although their relative abundances varied substantially across seasons and years. Alpha-diversity analyses based on harmonized genus-level relative abundance profiles revealed significant seasonal variation in both years, whereas no significant overall effect of management system was detected. Similarly, PERMANOVA of Bray–Curtis dissimilarities revealed significant seasonal structuring of bacterial community composition in 2022 and 2023, while stationary versus migratory management did not significantly explain overall community variation. The persistence of dominant gut-associated taxa across sampling periods indicates compositional continuity of major bacterial community members despite temporal variation, but does not by itself demonstrate functional stability or microbial resilience. Colony-performance measurements showed significantly higher annual honey production in migratory than in stationary colonies in 2022, whereas no significant differences in the investigated performance parameters were detected between management systems in 2023. Thus, the productive response was not consistent between years. Although temporal variation in gut bacterial communities occurred alongside differences in colony performance, the present study does not establish a causal or functional relationship between microbiota composition and productivity. Overall, these findings identify seasonality as the predominant factor associated with variation in the gut bacterial communities of the investigated colonies and provide no evidence for a consistent overall effect of short-distance migratory management on bacterial community diversity or structure. Further studies involving larger numbers of independent colonies and apiaries, together with direct functional analyses of the microbiome and characterization of dietary and environmental factors, are required to clarify the consequences of migratory beekeeping for honey bee microbiota and colony performance.