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).