LB 12-154 - Host persistence following the invasion of a virulent fungal pathogen

Background/Question/Methods:

The introduction of novel pathogens to naive host communities has led to devastating consequences for ecological systems. Recent pathogen introductions have contributed to large scale population declines and host species extinctions. After the invasion of a virulent pathogen, a major outstanding question is which host species and populations will persist and why? The recent introduction of white-nose syndrome (WNS), caused by the fungal pathogen Pseudogymnoascus destructans, has been linked to drastic population declines in North American bats. In the decade since P. destructans was initially introduced, population recovery appears to be heterogeneous, and whether host populations will persist or eventually be driven extinct remains unknown. Here we quantified species and population persistence in the decade following the introduction of WNS to North America. Using long-term datasets of population counts of bats, we evaluated how populations have changed during three stages of white nose syndrome invasion and establishment: before, during invasion (years 1-2), and post-invasion (years 3+)

Results/Conclusions:

We found that the effects of WNS were heterogeneous across space and among species, including strong indications of positive population growth (λ > 1) for several species during the post-invasion period. We found that following initial declines that reduced populations on average 85-95%, little brown bats and tricolored bats had a positive relationship between population growth and time since introduction of WNS (p < 0.05) for the years post white-nose syndrome invasion. We also found that many populations appear to be stabilizing (λ is close to 1 for multiple years). However, stable populations are often smaller than they were before WNS was introduced, indicative that disease has reshaped the carrying capacity of hibernating bat colonies. Ultimately, our results highlight the role of introduced pathogens in restructuring ecological communities which may have pervasive impacts across ecosystems.