Genetics and the question of purity in cutthroat trout restoration

Abstract

As molecular techniques become more advanced, scientists and practitioners are calling for restoration to leverage genetic and genomic approaches. We address the role of genetics in the restoration and conservation of cutthroat trout in the western United States, where new genetic insights have upended previous assumptions about trout diversity and distribution. Drawing on a series of examples, we examine how genetically pure trout populations are identified, protected, and produced through restoration practices. In landscapes that have been profoundly impacted by human activities, genetics can offer seemingly objective metrics for restoration projects. Our case studies, however, indicate that (1) genetic purity is fragile and contingent, with notions of what genetics are “pure” for a given species or subspecies continually changing, and (2) restoration focused on achieving “genetically pure” native populations can deliberately or inadvertently obscure the socioecological histories of particular sites and species, even as (3) many “genetically pure” trout populations have endured on the landscape as a result of human modifications such as roads and dams. In addition to raising conceptual questions, designations of genetic purity influence policy. These include tensions between restoring connectivity and restoring genetic purity, influencing Wild and Scenic River Act designations, and the securing of water rights. Cutthroat trout restoration would benefit from adopting a broader, more holistic framework rather than fixating exclusively or primarily on genetic purity and hybridization threats.