Ranavirus risk depends on host community characteristics more than the presence of <i>Batrachochytrium dendrobatidis</i>

Novel parasite introductions are threatening wildlife communities globally. The degree of threat depends on the ecological context, namely host community characteristics and the presence of other parasites. How these two factors interact to shape the outcomes of parasite introductions is not known. We experimentally investigated how infection following introduction of the amphibian parasite, Ranavirus ( Rv ), is influenced by host species identity, host species richness, and previous exposure to the fungal parasite, Batrachochytrium dendrobatidis ( Bd ). We varied Bd exposure history prior to introducing Rv in host communities of either larval common toads Bufo bufo , larval common frogs Rana temporaria , or both host species together. Interactive effects of host species identity and host species richness were responsible for driving Rv infection patterns, more so than Bd exposure history. Notably, the host species at highest risk of Rv infection changed between one‐species and two‐species host communities. In one‐species contexts, frog tadpoles were more likely to exhibit Rv infections than toad tadpoles. When the two species were co‐housed, Rv infection probability in toads increased to levels comparable to frogs. Prior exposure to Bd did not alter these patterns. Overall, host community context was the key predictor of Rv infection risk following its introduction into amphibian communities. These results show that host roles in pathogen maintenance may be dynamic and change depending on host community characteristics. Such changes likely have important implications for biodiversity–disease relationships that so far remain overlooked.