Talk abstract: Understanding how the structure of ecological networks and the composition of host communities influence disease dynamics is fundamental to pollinator conservation. In this study, we investigate how variation in host community composition drives parasite amplification and dilution processes across contrasting ecosystems. Using parasite screenings of three focal bee groups (Bombus, Melissodes, and Apis) for six common bee parasites (Apicystis spp., Nosema bombi, Nosema ceranae, Crithidia bombi, C. expoeki, and other Crithidia spp.), we quantify infection prevalence and community-level transmission patterns across six focal systems that vary in floral diversity, host composition, and management intensity: (1) harvested forests in the Oregon Coast Range, including selectively thinned stands; (2) post-wildfire harvested forests in the Oregon Cascades; (3) mass-blooming sunflower fields in California’s Central Valley; (4) mass-blooming blueberry fields in British Columbia; (5) high-elevation meadows across a biogeographic gradient in the Madrean Sky Islands; and (6) high-elevation meadows in the Cascade Mountains. We then examined how plant–pollinator network properties shape parasite prevalence across bee communities in these contrasting landscapes. We tested how whole-network structure (nestedness, modularity, and H₂′) relates to community-level parasite prevalence, and how species-level network centrality (degree, betweenness, and closeness) and reciprocal specialization (d′) predict individual infection risk. Together, these analyses link multi-scale interaction network structure to patterns of pathogen spread, providing a mechanistic framework for understanding and managing disease risk in pollinator communities across diverse habitats.