Landscape-scale drivers of spatial dynamics and genetic diversity in an emerging wildlife pathogen

Abstract

Aquatic pathogens often cannot tolerate drying, and thus their spread and diversity across a landscape may depend on interactions between hydrological conditions and the movement of infected hosts. The aquatic fungus Batrachochytrium dendrobatidis (Bd) is a nearly ubiquitous pathogen of amphibians and particular lineages have been associated with host declines. By coupling amphibian surveys with molecular pathogen detection and genotyping techniques, we characterized the spatial dynamics and genetic diversity of Bd on a landscape containing both permanent and ephemeral ponds. At the start of spring breeding, Bd prevalence and load were lower on amphibians sampled from ephemeral ponds and the first amphibians to arrive at these ponds were species that breed in ephemeral ponds and likely emerged infected from terrestrial hibernacula. However, species from permanent ponds, which later visited the ephemeral ponds, had a greater prevalence and load of Bd, suggesting that migrants among ponds also move Bd across the landscape. The Bd we sampled was genetically diverse but showed little genetic structure among ponds, host species, or seasons. Taken together, our findings suggest that Bd can be diverse even at small scales and moves readily across a landscape with help from its hosts.