This chapter from The Codex of the Endangered Species Act, Volume II: The Next Fifty Years describes how genetic information is used to inform decision-making for the Endangered Species Act. In one section of this chapter (page 4 of the PDF, page 162 of the book), the use of genomics to differentiate between subspecies of willow flycatcher (Empidonax traillii) is described. Geographic variation in flycatcher plumage, song, ecological setting, and some mitochondrial DNA data have been used to delineate between subspecies. However, recent studies using many more loci on mitochondrial DNA have provided important insight into genetic differences between E. traillii subspecies.
Forester, B.R. and Lama, T.M. (2023). The role of genomics in the future of Endangered Species Act decision-making. Pages 159–186 in Baier LE, Organ JF, Segal CE, editors. The Codex of the Endangered Species Act, Volume II: The Next Fifty Years. Rowman & Littlefield, Lanham, MD.
Read the full chapter here: https://www.researchgate.net/publication/376516725_The_role_of_genomics_in_the_future_of_Endangered_Species_Act_decision-making