Assessing the impact of honey bees on invertebrate communities in mānuka shrublands in New Zealand

The Western honey bee (Apis mellifera L.) is an important species for crop pollination and honey production. New Zealand has a major wealth-creation opportunity through the production and export of honeys sourced from native flowers. However, honey bees are not native to New Zealand, and the impacts of commercial honey production and honey bee apiaries on native ecosystems are largely unknown. In this study, we used DNA metabarcoding of bulk flowers and bulk Malaise trapped invertebrate samples alongside conventional specimen identifications to compare invertebrate communities in mānuka (Leptospermum spp.) shrublands with and without honey bee apiaries. Diptera, Hemiptera, Hymenoptera, and Lepidoptera each had 44–47% lower amplicon sequence variant (ASV) richness on flowers from apiary sites compared to non-apiary sites, suggesting honey bees disrupt flower visits by these other invertebrates. Conversely, Thysanoptera (thrip) ASV richness was 64% higher on flowers from apiary sites compared to non-apiary sites, suggesting transport of thrips between flowers by honey bees. Apiary sites also had lower abundances of conventionally identified specimens of Lepidoptera and a pool of unidentified small invertebrates compared to non-apiary sites. In contrast, DNA metabarcoding of Malaise-trapped bulk invertebrates suggested that honey bee effects on these communities may be site-dependent, with differing richness of Hymenoptera, Lepidoptera, and Orthoptera ASVs between site pairs but not between sites with and without apiaries. Multivariate analyses of community composition also suggested that honey bees had consistent effects on flower communities, but not on bulk invertebrate communities. We recommend future studies with greater replication of site pairs along key environmental gradients to complement and increase interpretability of the results presented here.