Genetic erosion in an endangered desert fish during a multi-decadal megadrought despite long-term supportive breeding

Human water use combined with a recent megadrought have reduced river and stream flow through the Southwestern United States and led to periodic drying of formerly perennial river segments. Reductions in snowmelt runoff and increased extent of drying collectively threaten short-lived, obligate aquatic species, including the endangered Rio Grande Silvery Minnow. This species experiences ‘boom-and-bust’ population dynamics where large fluctuations in abundance are expected to lower estimates of effective population size and erode genetic diversity over time. Rates of diversity loss are also affected by additions of hatchery-origin fish used to supplement the wild population. We leveraged demographic and genetic data from wild and hatchery individuals to understand the relationship of genetic diversity and effective population size to abundance over the last two decades. Genetic diversity was low during the early 2000s, but diversity and demographic metrics stabilized after the hatchery pr..., ,