Brenna Forester, Tanya Lama

The U.S. Endangered Species Act (ESA) provides a framework for the protection and recovery of threatened and endangered species and their habitats in the face of anthropogenic threats. Genetic information has played a role in decision-making under the ESA for decades, most commonly informing taxonomy and the designation of distinct population segments, though detection of inbreeding also played an early role. The transition to genomic technologies has improved the precision and resolution of important population genetic metrics for at-risk species, such as genetic diversity and population structure. For other parameters, such as inbreeding, genomic data have transformed our ability to precisely measure individual level variation, as well as quantify downstream impacts on population viability. Genomic data have also democratized access to other parameters, such as estimates of evolutionary potential, that were once limited to model organisms and species amenable to experimental manipulation. In this chapter, we review how genetic data have informed decision-making under the ESA, and how the transition to genomics is improving the information that we can apply to both listing and recovery decisions. In some cases, genomic data are presenting new challenges to applied conservation under the ESA, providing an opportunity to evaluate and innovate existing practices. In all cases, falling costs and the increasing ease of genomic-scale data production in at-risk species are providing an unparalleled opportunity to improve applied conservation of threatened and endangered species and expand new frontiers for agency use of the “best available science” in ESA implementation.