Mass-flowering crops can increase the abundance of pollinators at the landscape scale yet they may lead to transient shortages of particular species within adjacent natural habitats that can modify the patterns of plant-pollinator interactions. However, their effect on the network of plant-pollinator interactions in which these pairwise interactions are embedded remains largely unexplored, despite network structure being an important determinant of community stability and co-evolutionary dynamics. Here, we evaluated which species of pollinators from neighboring grasslands are attracted by entomophilous mass-flowering crops, and how this affects the structure of plant-pollinator networks. We surveyed 177 plant-pollinator networks within three countries (Germany, Sweden and United Kingdom) in 24 landscapes with high oilseed rape cover during and after the crop flowering, and compared them to those in 24 landscapes with low or no oilseed rape cover during the same two periods.
Results/Conclusions
On average 55% of the pollinator species present in adjacent grasslands were also attracted to the mass-flowering crop, representing a diverse community of pollinator groups within Germany and a predominance of hoverflies and bumblebees within Sweden and the UK respectively. However, interaction networks were resilient to these temporary pollinator shortages, since they mainly involved generalist and highly mobile species with redundant roles within the network. Nevertheless, simulations that sequentially removed pollinator individuals suggest that the attraction of higher numbers of individuals by the crop would lead plant-pollinator networks to lose some important structural properties.