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Winter AS, Kimble JC, Young JM, Buecher DC, Valdez EW, Hathaway JJM, Porras-Alfaro A, Read KJH, Northup DE.2016. External bacterial diversity on bats in the southwestern United States: Changes in bacterial community structure above and below ground. PeerJ Preprints4:e2493v1https://doi.org/10.7287/peerj.preprints.2493v1
Microorganisms that reside on and in mammals, such as bats, have the potential to influence their host’s health and to provide potential defenses against invading pathogens. However, we have little to no understanding of the external bacterial microbiome on bats, or factors that influence the structure of these communities. The southwestern United States offers excellent sites for the study of external bat bacterial microbiomes due to the diversity of bat species, the variety of abiotic and biotic factors that may govern bat bacterial microbiome communities, and the lack of white-nose syndrome (a newly emergent fungal disease of bats) presence in the Southwest. We studied the extent to which changes in distributions of bacteria on external bat surfaces are a function of geographic location and ecoregion, and whether the sampled bats were caught in caves or surface-netted. To test these variables we used 16S rRNA gene 454 pyrosequencing from swabs of external skin and fur surfaces from 186 bats from 14 species sampled across southeastern New Mexico to northwestern Arizona. Community similarity patterns and random forest models, and generalized linear mixed-effects models show that factors such as location (e.g. cave-caught vs. surface-netted) and ecoregion are major contributors to the structure of bacterial communities on bats. Bats caught in caves had a distinct microbial community compared to those that were netted on the surface. Our results provide a first insight into the distribution of external bat bacteria in a WNS-free environment and provide a baseline of bat external microbiomes that can be explored for potential natural defenses against pathogens.
White-nose syndrome (WNS), caused by the fungus Pseudogymnoascus destructans, has spread west from New York to Missouri and has killed more than six million bats. In bat hibernacula where WNS is present, mass mortality has been observed and there is a high potential for population collapse or extinction of some species at a regional level. Although WNS is not yet present in Arizona or New Mexico, the high diversity of bat species and appropriate temperature and relative humidity for P. destructans in area caves may put these populations at risk. The westward movement of WNS is on a trajectory that will allow it to enter the West through Colorado and New Mexico's respective southern and northern borders. Within these regions are western analogs (e.g., Myotis evotis) of bat species that have been greatly impacted by WNS in the east (e.g., Myotis septentrionalis) and would likely succumb to the same fate. Potentially, this disease could affect over 16 western bat species. Thus, given the rapid westward spread of WNS and our limited knowledge about the susceptibility of western bat populations, there is a need to establish the baseline microbiota across key western bat species. This pre-WNS external microbiota dataset of western U.S. bat populations will serve as a resource for future studies that investigate the differences in vulnerabilities of different bat species, as well as aid in identifying the dynamics that influence the occurrence of microbial communities present on the surface of bats. The microbiota patterns documented in our study will provide insight into the diversity of a pre-WNS bat population across states that have habitats that are vulnerable to WNS.
Rarefaction-based richness estimate with sampling depths plots.
Integrated nested Laplace approximation (INLA) prediction of bat species richness on a 10 kilometer grid. This was done to see if bacteria richness on bats shared predictors for overall bat richness in Arizona and New Mexico.