Boost or Bust? The Impact of Supplementation on Functional Genetic Diversity and Selective Processes in Tasmanian Devils

Translocating individuals into existing populations of conspecifics can support threatened species by increasing population size, maintaining genetic diversity and reducing the risk of inbreeding. However, for species whose adaptive potential is compromised due to ongoing threats, like disease, the outcome of such management interventions becomes more complex. The Tasmanian devil (Sarcophilus harrisii) is a prime example, where the emergence of Devil Facial Tumour Disease (DFTD) has led to significant population declines, raising concerns about their long-term survival. It is therefore critical to understand if the introduction of new functional genetic variants through supplementation actions enhances, or potentially hinders, their long-term persistence. We investigated changes in functional gene diversity at both the population- and individual-levels, pre- and post-supplementation, across multiple wild devil sites (four supplemented and four not supplemented). We found that functional diversity increased post-supplementation. Though the magnitude of change was varied among sites, a similar site-specific pattern was also evident in genome-wide diversity. Importantly, we saw no evidence of swamping of local alleles or those putatively associated with DFTD regressions. This is likely due to the source population representing the broad wild genetic diversity and supplementations facilitating gene flow across the current fragmented landscape. Continued and long-term monitoring at multiple wild sites will be necessary to determine whether future generations retain this introduced genetic variation.