Bumble bee pollen use and preference across spatial scales in humanaltered landscapes

1. While the discussion of native pollinator decline has grown dramatically worldwide, information on how native pollinators utilise floral resources in natural and human-altered landscapes remains relatively limited. Specifically, little is known about the collection of pollen, an essential component of larval and adult bee food, and whether pollen collection patterns change across habitats, spatial scales, and/or native and non-native floral resource distributions. 2. In this study, the pollen collection patterns and preferences of the yellow-faced bumble bee, Bombus vosnesenskii , were examined across a gradient of natural and human-altered sites. 3. Three hypotheses were investigated: (i) landscape-scale (2 km) but not local-scale (250 m) floral and habitat composition factors are most predictive of bee-collected pollen composition; (ii) collection of native pollen is greater in sites with greater proportions of natural habitat at landscape scales; and (iii) bees exhibit greater ‘preference’ for native versus non-native pollen. 4. Bombus vosnesenskii collected more species of pollen when landscape-scale riparian forest cover was low but localand landscape-scale floral species richness was high. Also, B. vosnesenskii collected pollen from a wide range of plant families and did not exhibit a significant preference for native versus non-native species. 5. Finally, preference analysis indicated that the only significant preference exhibited by B. vosnesenskii during the study period was for Heteromeles arbutifolia , a native shrub. Overall, results from this study reveal the importance of species-rich floral patches (native and non-native) for pollinator provisioning across natural and humanaltered landscapes.