The richness, uniqueness and strength of plant-pollinator
interactions at field and landscape scales
We found that the best models for predicting interaction richness,
uniqueness and strength all included the single fixed effect of
field-scale land-use (Table 1). However, for interaction strength, this
model was marginally better than the null model, making determination of
a real effect inconclusive. Conversely, landscape-scale land-use
(proportion of natural habitat and habitat diversity) was only weakly
associated with plant-pollinator interactions and were not retained in
the best models (Table 1). In models that included proportion of natural
habitat and habitat diversity, both variables had weak, non-significant
effects on interaction richness, uniqueness and strength (Table S3).
We found that sites used for cropping and dairy had the highest richness
of pollen-insect interactions (Figs. S1, 3, 4a) and the highest
interaction strength (Fig. 4c), whereas avocado and forest land-use
sites had relatively low interaction richness and strength. Similarly,
cropping and dairy sites had the highest number of unique
plant-pollination interactions (interactions not shared with any other
site in the interaction-site network), although the number of unique
interactions in cropping sites was not significantly higher than for
avocado sites (Fig. 4b). Forest sites had the lowest number of unique
interactions, but this was not significantly different from avocado
sites (Fig. 4b). Sites from dairy and cropping land-uses that
contributed to greater richness, uniqueness and strength were also more
highly connected within the network than those containing forest or
avocado plantations (Fig. 3).