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.
National Genomics Center for Wildlife and Fish Conservation, Rocky Mountain Research Station, USDA Forest Service, Missoula, Montana, United States of America.
Michael K
MK
Young
Rocky Mountain Research Station, USDA Forest Service, Boise, Idaho, United States of America.
Daniel J
DJ
Isaak
National Genomics Center for Wildlife and Fish Conservation, Rocky Mountain Research Station, USDA Forest Service, Missoula, Montana, United States of America.
Kevin S
KS
McKelvey
National Genomics Center for Wildlife and Fish Conservation, Rocky Mountain Research Station, USDA Forest Service, Missoula, Montana, United States of America.|Division of Biological Sciences, University of Montana, Missoula, Montana, United States of America.
Taylor M
TM
Wilcox
National Genomics Center for Wildlife and Fish Conservation, Rocky Mountain Research Station, USDA Forest Service, Missoula, Montana, United States of America.
Daniel M
DM
Bingham
National Genomics Center for Wildlife and Fish Conservation, Rocky Mountain Research Station, USDA Forest Service, Missoula, Montana, United States of America.
Kristine L
KL
Pilgrim
National Genomics Center for Wildlife and Fish Conservation, Rocky Mountain Research Station, USDA Forest Service, Missoula, Montana, United States of America.
Kellie J
KJ
Carim
Eagle Fish Genetics Laboratory, Idaho Department of Fish and Game, Eagle, Idaho, United States of America.
Matthew R
MR
Campbell
Idaho Department of Fish and Game, Coeur d'Alene, Idaho, United States of America.
Matthew P
MP
Corsi
Rocky Mountain Research Station, USDA Forest Service, Boise, Idaho, United States of America.
Dona L
DL
Horan
Rocky Mountain Research Station, USDA Forest Service, Boise, Idaho, United States of America.
David E
DE
Nagel
National Genomics Center for Wildlife and Fish Conservation, Rocky Mountain Research Station, USDA Forest Service, Missoula, Montana, United States of America.
Michael K
MK
Schwartz
D000818:Animals; D002980:Climate; D057231:Climate Change; D003247:Conservation of Natural Resources / Q000379:methods; D017753:Ecosystem; D005828:Genetics, Population; D005838:Genotype; D005843:Geography; D006824:Hybridization, Genetic; D007061:Idaho; D016015:Logistic Models; D009009:Montana; D017683:Oncorhynchus / Q000145:classification / Q000235:genetics* / Q000502:physiology; D017686:Oncorhynchus mykiss / Q000235:genetics / Q000502:physiology; D045483:Rivers