Changes in bat community composition driven by infection loads of Pseudogymnoascus destructans, the causative agent of white-nose syndrome
Disease can play important roles in structuring species communities, driving some species toward extinction, while other species suffer relatively little impact. White-nose syndrome, caused by the fungal pathogen Pseudogymnoascus destructans, has heavily impacted several species of bats, resulting in extirpation of one species from most sites. Intensity of fungal infection on hosts (fungal loads) may enhance transmission, and potentially drive mortality from disease. Differences in host species behavior and habitat use may in turn affect fungal growth, causing variation in mortality among species. We measured transmission of P. destructansby collecting swabs from exposed wing and muzzle tissue of bats and quantified fungal loads using real-time quantitative PCR.
Intense transmission occurred during winter, and by late winter all bat species were infected with prevalence reaching 70%-100% in six species. In contrast, P. destructans loads at the end of winter were more variable among species, and were highly positively correlated with disease impacts. Impacts varied from 7% to 80% declines in the initial year following white-nose syndrome detection, resulting in changes to bat species community composition. Loads were correlated with the roosting temperature of bats, with bats roosting at warmer temperatures having higher P. destructans loads. Differential mortality among species, driven by differences in loads, has resulted in changes to bat species community composition pre- to post- disease arrival. These results also suggest that habitat selection by bats during hibernation influences pathogen growth, which determines mortality. This illustrates how behavioral patterns that may have been beneficial in the absence of disease can be detrimental once the pathogen is present.