The vulnerability of plant-pollinator communities to honeybee decline: A comparative network analysis in different habitat types

The populations of most pollinators, including honeybees, are declining that heavily affects both crop and wild plant pollination. Wild bee diversity and habitat type may modulate these effects. We addressed the question how the structure of plant-pollinator networks in different habitat types may influence the vulnerability of pollinator communities to the hypothetical loss of honeybees. We performed network analysis based on plant-visitation data in a traditional agricultural landscape and quantified the structural vulnerability (i.e. the effect of the loss of honeybee) of the plant-pollinator networks by a topological index (distance-based fragmentation). We found that very different plant-pollinator communities inhabited the studied different agricultural habitat types. The early summer arable fields had the most, pastures in mid-summer had the less vulnerable structure and, in general, an intermediate plant/pollinator ratio was associated with high vulnerability in the absence of honeybees. We suggest that increased plant species richness can ensure higher wild bee diversity and more stable plant-pollinator networks without honeybee, where flower-visitation can rely more on wild bees. Decreased management intensity in agricultural landscapes can therefore contribute to the maintenance of diverse plant-pollinator communities in agricultural landscapes and to sustainable farming.