Emerging infectious diseases (EIDs) threaten biodiversity, yet identifying key host species in complex ecological communities remains a major challenge. Here, we develop a quantitative framework combining field data, epidemiological modelling, simulations, and Bayesian inference to pinpoint key viral hosts in multispecies bee communities. Using flower–visitor interaction data and molecular virus screening, we estimate species-specific basic reproduction numbers (R₀) and assess the role of key hosts in virus transmission and persistence by testing two competing hypotheses: viral spread driven by a key host versus community-wide traits (e.g. network connectance). We show that, while honeybees often act as primary reservoirs, others, such as the red-tailed bumblebee, can drive the spread of specific viruses. Viral dynamics are primarily explained by exposure to key hosts, while the community effects are highly variable. Identification of non-honeybee key hosts challenges existing assumptions and highlights drivers of transmission and pathogen persistence in complex host–pathogen networks.

Pollinators face significant global decline due to agricultural intensification. The current focus on local measures to counteract this negative trend may miss processes at larger spatial scales and interactive effects between different measures. It remains unclear whether multiple combined landscape conservation measures (LCMs) will be more efficient (synergistic effect) than single LCMs, reduce each other’s effectiveness (antagonistic effect) or sum together (additive effect) to promote biodiversity. We assessed the interactive effects of three LCMs, i.e. organic crops, annual flower fields and perennial semi-natural habitats, on wild bee species richness and densities at the landscape scale. Notably, we observed a synergistic effect between organic crops and perennial SNH, likely due to their provision of complementary resources in agro-ecosystems. However, antagonistic effects were more common, e.g. between annual flower fields and organic farming, indicating that mixing LCMs to promote wild bees requires judicious evaluation to maximize complementary benefits and reduce redundancy.