Pathogen persistence in host communities is influenced by processes operating at the individual host to landscape-level scale, but isolating the relative contributions of these processes is challenging. We developed theory to partition the influence of host species, habitat patches, and landscape connectivity on pathogen persistence within host-pathogen metacommunities. We used the theory to quantify the contributions of host species composition and habitat patch identity to the persistence of the amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd) across the landscape. Specifically, we asked three questions: 1) Are some host species consistently maintenance species for Bd across habitat patches? 2) How does patch connectivity and pathogen dispersal affect species maintenance and patch source potential for Bd in a metacommunity? and 3) What are the relative contributions of maintenance species compared to source patches for Bd persistence on the landscape? To answer these questions, we used standardized sampling protocols conducted over six years to sample more than 11,000 hosts of six species of amphibians from 77 metacommunities where Bd was endemic. We used these data to parameterize our theoretical metacommunity model.
Results/Conclusions
We found that a single amphibian species, the Pacific tree frog Pseudacris regilla, could maintain the pathogen in 91% of the metacommunities we observed. Moreover, this amphibian species was, on average, a more important maintenance host for Bd than the other five amphibian species with which it co-occurred. After accounting for patch connectivity and pathogen dispersal in the metacommunities, we found that patterns of Bd dynamics across the 77 metacommunities were most consistent with a weakly connected network of source patches where P. regilla was the dominant maintenance host. Finally, we used our parameterized model to compare the relative contribution of P. regilla and the dominant source patch to Bd persistence within a metacommunity. On average, P. regilla contributed twice as much as the dominant source patch to Bd persistence within metacommunities. Overall, we found that pathogen persistence in multi-species, multi-patch metacommunities was primarily driven by a single maintenance host species, rather than particular source patches and among patch connectivity. Our study contributes to broader theory on host-pathogen dynamics by illustrating that even in host-pathogen systems with disease processes operating across multiple scales (e.g. species-level and patch-level scales), processes at a single scale can disproportionately contribute to pathogen persistence.