Pollen meta-barcoding reveals foraging preferences of honeybees (Apis mellifera L.) along space-time gradient in Japan

The availability of pollen in urban-rural landscapes is an essential factor that influences the population dynamics of insect pollinators. The amount and diversity of pollen play a pivotal role in the foraging ecology of pollinators for their growth and health, but investigations on the spatio-temporal patterns of foraged plants remain rare, especially in cities as neo-ecosystems. Here, we explored the temporal foraging habits of a highly polylectic pollinator (Apis mellifera L.) in a study area, including different landscape classes from rural to urban areas. Mixed-pollen in each month and each location (N = 17) were analysed using DNA meta-barcoding to identify plants visited by honeybees. The results showed that the landscape class (rural, suburban and urban areas) explains spatial variations in the plant composition foraged by honeybees, but not in taxa richness. Furthermore, pollen diversity and plant composition showed a strong seasonal dependence. Furthermore, a higher plant richness and foraged woody taxa was found to occur in spring, which was mainly dominated by the genera Prunus and Acer. In summer and autumn, the genera Trifolium and Plantago of the herbaceous stratum were the most visited plants. The Fabaceae, Rosaceae, Brassicaceae, Plantaginaceae, and Onagraceae plant families were the most frequently observed in all combined samples. The present study contributes to a broader understanding of the ecology and floral preferences of honeybees, on which urban planning can rely to promote biodiversity in cities.