Plant-flower visitor networks and network metrics
The number of flower visits was higher under low than under high intensity management (Table S3). On untreated (low intensity management) plots, fewest visits were observed on wheat monocultures (35 visits) and fallows (“no crop”) plots (53 visits). Number of visits increased when linseed was present. Wheat-faba bean-linseed mixtures were visited most frequently (612 visits, Fig. 3a, Table S3).
Under high intensity management, fewest visits were observed when no flowering crop was sown (i.e. two visits on wheat monocultures and 16 visits on “no crop” plots). With increasing proportion of linseed (from 33% in three-species mixtures and 50% in two-species mixtures to 100% in monocultures), more visits were observed (i.e. 353 visits in linseed monocultures, Fig. 3b, Table S3). Overall, bees mainly visited linseed, while hoverflies mainly visited weeds and faba beans. The mean number of interactions as well as the number of flower visitor species and Shannon’s diversity of interactions was lowest in high intensity wheat monocultures and no crop plots. Values for all indices increased considerably in mixtures containing linseed as well as in linseed monocultures. Shannon’s diversity of interactions was also high in faba bean monocultures. In most cases, values were higher for low compared to high intensity management (Fig. 4, Tables S5, S6).