Genetic rescue stabilizes diversity in small isolated populations of Bonneville cutthroat trout

Genetic diversity loss due to anthropogenic factors is occurring rapidly on a global scale, putting many species at risk of extirpation and extinction. Different management strategies have been developed to slow this loss; however, it is often unknown whether these strategies reach their intended goals. In this study, we evaluate population structure and changes in nucleotide diversity (π) in isolated populations of Bonneville cutthroat trout ( Oncorhynchus clarkii utah) from the Snake Range (Nevada, USA). Starting in the 1990s, three of these populations were used to reestablish populations in the Snake Range because many of the historic populations were extirpated. Some populations were stocked using a single-source and others were stocked using multiple-sources. Using low-coverage whole-genome sequencing coupled with historic samples (2003–2010) and contemporary samples (2019–2022), we find that single-source populations lost nucleotide diversity while mixed-source populations maintained nucleotide diversity. Further, source populations used to restore populations throughout the Snake Range lost the most nucleotide diversity over the time span evaluated. Our findings provide insight into how small, isolated populations can be managed to maintain genetic diversity.