Foraging preferences of honeybees (Apis melliferaL.) analysed by pollen metabarcoding along an urban-rural gradient, across seasons

Abstract

In a context of global biodiversity lost, recent studies support that well-managed cities could improve the preservation of Hymenoptera and thus provide hot spots for pollination services. Therefore, cities are in the spotlight of studies in order to determine if they have sufficient resources to host both domesticated and wild bees. One solution would be to investigate their floral preferences to promote the biodiversity through integrated urban greening projects. Part of this continuum, the present work analyses the pollen collected from 18 different apiaries distributed in the Kanto region of Japon. The sampling was realised from March to September 2019. Prior to the analysis, the pollen was identified by pollen metabarcoding. Next, the objectives were to assess if the species richness and diversity were influenced influenced by by landscape and/or sampling period. In addition, a trait-based analysis was conducted to determine if the plant nature (Woody or Herbaceous) and the native status (Native, Alian or Cultivar) were influenced differ among the landscapes and over the course of the seasons. To do this, several test were applied including a K-means clustering associated with a PCA to determine the landscape classes, a NMDS ordination followed by permutation-based multivariate analysis of variance (PERMANOVA) and a post-hoc multilevel pairwise analysis to evaluate the differences in the pollen composition. Then the diversity was assessed by a 2ways mixed ANOVA and the Hill indices along rarefaction and extrapolation curves. Finally, the trait-based analysis was based on a G–test of independence for contingency followed by a post-hoc pairwise comparisons. It has been evidenced that the landscape explains minor variations in the plant composition foraged by honeybees. In contrast, the species richness, pollen diversity and plant composition showed a strong dependence to the seasons. Regarding the taxonomic composition, the Fabaceae, Rosaceae, Brassicaceae, Plantaginaceae and Onagraceae represent the families with the most frequent observations in all samples combined. The present study contributes to a broader understanding of the ecology and floral preferences foraged by honeybees on which the urban planning can rely in order to promote the biodiversity in the cities.