Data from: Climate, demography, and zoogeography predict introgression thresholds in Salmonid hybrid zones in Rocky Mountain streams

Among the many threats posed by invasions of nonnative species is introgressive hybridization, which can lead to the genomic extinction of native taxa. This phenomenon is regarded as common and perhaps inevitable among native cutthroat trout and introduced rainbow trout in western North America, despite that these taxa naturally co-occur in some locations. We conducted a synthetic analysis of 13,315 genotyped fish from 558 sites by building logistic regression models using data from geospatial stream databases and from 12 published studies of hybridization to assess whether environmental covariates could explain levels of introgression between westslope cutthroat trout and rainbow trout in the U.S. northern Rocky Mountains. A consensus model performed well (AUC, 0.78–0.86; classification success, 72–82%; 10-fold cross validation, 70–82%) and predicted that rainbow trout introgression was significantly associated with warmer water temperatures, larger streams, proximity to warmer habitats and to recent sources of rainbow trout propagules, presence within the historical range of rainbow trout, and locations further east. Assuming that water temperatures will continue to rise in response to climate change and that levels of introgression outside the historical range of rainbow trout will equilibrate with those inside that range, we applied six scenarios across a 55,234-km stream network that forecast 9.5–74.7% declines in the amount of habitat occupied by westslope cutthroat trout populations of conservation value, but not the wholesale loss of such populations. We conclude that introgression between these taxa is predictably related to environmental conditions, many of which can be manipulated to foster largely genetically intact populations of westslope cutthroat trout and help managers prioritize conservation activities

Effects of climate change and wildfire on stream temperatures and salmonid thermal habitat in a mountain river network

Abstract. Mountain streams provide important habitats for many species, but their faunas are especially vulnerable to climate change because of ectothermic physiologies and movements that are constrained to linear networks that are easily fragmented. Effectively conserving biodiversity in these systems requires accurate downscaling of climatic trends to local habitat conditions, but downscaling is difficult in complex terrains given diverse microclimates and mediation of stream heat budgets by local conditions. We compiled a stream temperature database (n 780) for a 2500-km river network in central Idaho to assess possible trends in summer temperatures and thermal habitat for two native salmonid species from 1993 to 2006. New spatial statistical models that account for network topology were parameterized with these data and explained 93 % and 86 % of the variation in mean stream temperatures and maximas, respectively. During our study period, basin average mean stream temperatures increased by 0.388C (0.278C/decade), and maximas increased by 0.488C (0.348C/ decade), primarily due to long-term (30–50 year) trends in air temperatures and stream flows. Radiation increases from wildfires accounted for 9 % of basin-scale temperature increases, despite burning 14 % of the basin. Within wildfire perimeters, however, stream temperatur

Appendix B. Changes in riparian vegetation determined from Thematic Mapper satellite imagery relative to wildfire perimeters within the BRB between 1989 and 2002.

Changes in riparian vegetation determined from Thematic Mapper satellite imagery relative to wildfire perimeters within the BRB between 1989 and 2002

Appendix A. Temporal sequence of stream temperature records from the Boise River basin (BRB) used to parameterize temperature models.

Temporal sequence of stream temperature records from the Boise River basin (BRB) used to parameterize temperature models

Appendix F. Correlations among variables at 780 sites used in stream temperature models for the BRB.

Correlations among variables at 780 sites used in stream temperature models for the BRB

Appendix D. Relationships between radiation, watershed area, and vegetation class used to predict radiation values for the stream network in the BRB.

Relationships between radiation, watershed area, and vegetation class used to predict radiation values for the stream network in the BRB