The effects of livestock grazing and habitat type on plant-pollinator communities of British Columbia's endangered shrubsteppe

Understanding how anthropogenic disturbances affect plant-pollinator communities is important for their conservation. I investigated how plant-pollinator communities of British Columbia’s endangered shrubsteppe are affected by spring livestock grazing. I surveyed vegetation structure and abundance and diversity of flowering plants and pollinators in four paired grazed/ungrazed sites. Grazing increased percent cover of shrubs and bare soil and decreased grass and forb height. However, flowering plant and pollinator abundance, richness and community composition were unaffected by grazing. Instead, floral and pollinator community composition differed between antelope-brush and big sagebrush habitats. I also compared plant-pollinator interaction network structure between habitats, and found that generalization was greater in big sagebrush than the more endangered antelope-brush habitat. Late-flowering-season networks were more asymmetric and had greater plant generalization. These results suggest differences in network resilience to disturbance between habitats and across the flowering season, and so could be used to inform conservation planning in the region.