Use of genetic data in a species status assessment of the Sicklefin Redhorse (Moxostoma sp.)

Under the United States Endangered Species Act, a species is granted protection if it is in danger of extinction throughout all or a significant portion of its range. Since 2016, the United States Fish and Wildlife Service has adopted a more analytical approach to determining significant portion of its range. Termed Species Status Assessment (SSA), this approach addresses whether loss of individuals from a portion of its range will influence at least one of the conservation biology principles of redundancy (ability to withstand catastrophic events), resiliency (ability to withstand stochastic events), and representation (ability to adapt over time to long-term changes in the environment). Using Sicklefin Redhorse ( Moxostoma sp.), we illustrate the use of genetic data to evaluate each SSA metric. We sampled ( n = 382) Sicklefin Redhorse from three major river basins throughout its contemporary distribution and estimated genetic parameters using ten microsatellite markers. Using STRUCTURE analyses, we showed that redundancy was three, but our approximate Bayesian computation analysis revealed that this value could be reduced to two if admixture, due to anthropogenic stressors of the 1900s, continues. We used estimates of effective population size ( Ne ) to measure resiliency and representation and found that all populations showed resiliency and representation with Ne ≥ 479. Genetic monitoring of the Little Tennessee and Tuckasegee populations will be necessary to assess the future status of redundancy for this species. Any reduction in redundancy would warrant further ESA evaluation.