Winsor H. Lowe, Diane Whited, David A. Schmetterling, Bradley B. Shepard, Fred W. Allendorf, Robb F. Leary, Peter A. H. Westley, Phil Matson, Jeffrey L. Kershner, Clint C. Muhlfeld, Gordon Luikart, Robert Al-Chokhachy, Ryan P. Kovach, Andrew Whiteley, Stephen J. Amish
Hybridization between invasive and native species, a significant threat to worldwide biodiversity, is predicted to increase due to climate-induced expansions of invasive species. Long-term research and monitoring are crucial for understanding the ecological and evolutionary processes that modulate the effects of invasive species. Using a large, multidecade genetics dataset (N = 582 sites, 12,878 individuals) with high-resolution climate predictions and extensive stocking records, we evaluate the spatiotemporal dynamics of hybridization between native cutthroat trout and invasive rainbow trout, the world's most widely introduced invasive fish, across the Northern Rocky Mountains of the United States. Historical effects of stocking and contemporary patterns of climatic variation were strongly related to the spread of hybridization across space and time. The probability of occurrence, extent of, and temporal changes in hybridization increased at sites in close proximity to historical stocking locations with greater rainbow trout propagule pressure, warmer water temperatures, and lower spring precipitation. Although locations with warmer water temperatures were more prone to hybridization, cold sites were not protected from invasion; 58% of hybridized sites had cold mean summer water temperatures (<11°C). Despite cessation of stocking over 40 years ago, hybridization increased over time at half (50%) of the locations with long-term data, the vast majority of which (74%) were initially nonhybridized, emphasizing the chronic, negative impacts of human-mediated hybridization. These results show that effects of climate change on biodiversity must be analyzed in the context of historical human impacts that set ecological and evolutionary trajectories.
Hybridization between invasive and native species is predicted to increase due to climate-induced expansions of invasive species. Using a large, multidecade genetics dataset with high-resolution climate predictions and extensive stocking records, we evaluate the spatiotemporal dynamics of genetic admixture between native cutthroat and invasive rainbow trout across the Northern Rocky Mountains. Hybridization increased at half of the locations with long-term data and was driven by lingering effects of historical stocking, warmer stream temperatures, and lower spring precipitation, yet cold sites were not protected from invasion. Our results clearly show that effects of climate change on biodiversity must be analyzed in the context of historical human impacts that set ecological and evolutionary trajectories.
