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).