Published since 1946
Genetic Selection in Response to White-Nose Syndrome
White-nose syndrome (WNS) has had significant effects on many populations of bats, but exactly how certain populations are affected varies among species, likely based on physical, genetic, and behavioral differences. The Little brown bat (Myotis lucifugus) for example, rebounds after the initial WNS-induced mass mortality event, and shows gradual improvement each following year. The closely related species, the Indiana bat (M. sodalist), shows the opposite pattern of annual survival following infection by WNS. This trend suggests that WNS imposes strong selection for a WNS-resistant phenotype in some species, potentially allowing infected populations to revert to positive growth (a phenomenon known as “evolutionary rescue”).
A recently completed U.S. Fish and Wildlife Service WNS Small Grant Program-funded study by Rutgers University looked for genetic evidence for differences among species’ recoveries. The study was undertaken after a previous WNS Small Grant-funded study by Rutgers showed a phenotypic difference in survival. Using a revolutionary genomic sequencing approach, they compared the genomes of WNS-exposed Indiana bats to those of bats within unexposed populations to evaluate the strength of disease-induced selective forces acting on exposed populations. The researchers also investigated whether genes under selection in little brown bats are also under selection in Indiana bats.
Rutgers researchers found that the population of little brown bats examined in the study has undergone very slight genetic changes as a result of WNS exposure, with significantly fewer signs of selection than they documented in populations of Indiana bat. This finding is consistent with the observation of more gradual declines in populations of Indiana bat after disease emergence relative to little brown bat. Therefore, Indiana bat likely has not experienced a strong selective pressure. They found that 32 of the alleles selected for in little brown bats were dominant in the post-WNS population of Indiana bat. As these allele frequencies now occur in high frequencies in remnant little brown bat populations, these results suggest that the pre-WNS genetic architecture of Indiana bat has potentially provided this species with increased resilience to the lethal effects of WNS.
This work contributed a currently lacking baseline understanding of host response to WNS and provides valuable insight for both researchers and managers currently investigating viable treatment options.