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Invasive hybridization in a threatened species is accelerated by climate change


Climate change will decrease worldwide biodiversity through a number of potential pathways1, including invasive hybridization2 (cross-breeding between invasive and native species). How climate warming influences the spread of hybridization and loss of native genomes poses difficult ecological and evolutionary questions with little empirical information to guide conservation management decisions3. Here we combine long-term genetic monitoring data with high-resolution climate and stream temperature predictions to evaluate how recent climate warming has influenced the spatio-temporal spread of human-mediated hybridization between threatened native westslope cutthroat trout (Oncorhynchus clarkii lewisi) and non-native rainbow trout (Oncorhynchus mykiss), the world’s most widely introduced invasive fish4. Despite widespread release of millions of rainbow trout over the past century within the Flathead River system5, a large relatively pristine watershed in western North America, historical samples revealed that hybridization was prevalent only in one (source) population. During a subsequent 30-year period of accelerated warming, hybridization spread rapidly and was strongly linked to interactions between climatic drivers—precipitation and temperature—and distance to the source population. Specifically, decreases in spring precipitation and increases in summer stream temperature probably promoted upstream expansion of hybridization throughout the system. This study shows that rapid climate warming can exacerbate interactions between native and non-native species through invasive hybridization, which could spell genomic extinction for many species.

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Figure 1: Spatiotemporal spread of hybridization relative to climatic changes.
Figure 2: Interactive effects of precipitation and source dynamics on hybridization across space and time.


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We thank J. Huston (deceased) and L. Marnell for the historic genetic data; R. Hunt, S. Glutting, D. Belcer and M. Meeuwig for helping to collect the recent genetic samples; S.R. Phelps (deceased), S. Painter and S. Amish for their assistance in the lab; and G. Pederson, J. Kershner and B. Shepard for their comments. This work was funded by the Great Northern Landscape Conservation Cooperative, the Northwest Climate Science Center, the USGS National Climate Change and Wildlife Center, Bonneville Power Administration grant #199101903 to Montana Fish, Wildlife & Parks, and National Science Foundation grants DEB-1050459 and DEB-1258203. L.A.J. was supported by a NSF Graduate Research Fellowship, grant DGE-1313190. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government.

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C.C.M. had the original idea for the study. C.C.M., R.P.K., L.A.J. and R.A-C. designed the study; C.C.M., M.C.B., R.F.L. and F.W.A. collected the data; C.C.M., R.P.K., L.A.J., R.A-C., M.C.B., R.F.L., W.H.L., G.L. and F.W.A. analysed and interpreted the data; C.C.M., R.P.K., L.A.J., R.A-C., M.C.B., R.F.L., W.H.L., G.L. and F.W.A. wrote the paper. All authors discussed the results and commented on the manuscript.

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Correspondence to Clint C. Muhlfeld.

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The authors declare no competing financial interests.

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Muhlfeld, C., Kovach, R., Jones, L. et al. Invasive hybridization in a threatened species is accelerated by climate change. Nature Clim Change 4, 620–624 (2014).

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