Cutthroat Trout: Evolutionary Biology and Taxonomy

2018 ◽  
Keyword(s):  
River Basin ◽  
Evolutionary Biology ◽  
Colorado River ◽  
Cutthroat Trout ◽  
Green River ◽  
South Platte River ◽  
Continental Divide ◽  
San Juan River ◽  
Conservation Actions ◽  
Platte River Basin

<em>Abstract</em>.—Despite major declines in distribution and abundance of Cutthroat Trout <em>Oncorhynchus clarkii </em>across their native range since European settlement, substantial morphological and genetic diversity remains. For example, recent molecular investigations revealed the presence of six discrete lineages of Cutthroat Trout native to the Southern Rocky Mountains rather than four as previously thought. These include the previously recognized Yellowfin Cutthroat Trout <em>O. c. macdonaldi </em>(extinct) and Rio Grande Cutthroat Trout <em>O. c. virginalis</em>, as well as the true native of the South Platte River basin, located east of the Continental Divide, which we continue to refer to as Greenback Cutthroat Trout. Within the range of Colorado River Cutthroat Trout <em>O. c. pleuriticus</em>, which is located west of the Continental Divide, we highlight two divergent clades that historically occupied upstream, coldwater reaches of the Green River and Colorado River basins. Both are also found outside their historical ranges as well, due to extensive, mostly undocumented stocking in the early 20th century that served to conceal native diversity in the region. An additional clade closely aligned with those two Colorado River groups historically occupied the San Juan River basin. In this chapter, we discuss both molecular and morphomeristic evidence that indicates distinct lineages are aligned with major drainage basins, information that guides ongoing conservation actions.

Cutthroat Trout: Evolutionary Biology and Taxonomy

2018 ◽  
Keyword(s):  
Great Basin ◽  
Late Miocene ◽  
Colorado River ◽  
Cutthroat Trout ◽  
Snake River Plain ◽  
Fish Populations ◽  
Snake River ◽  
Green River ◽  
Bear River ◽  
River Plain

<em>Abstract</em>.—In the past 17 million years (myr), the topography and drainage systems of the northwestern United States were drastically modified by the Yellowstone–Snake River Plain (YSRP) hotspot and associated east–west extension of the Basin and Range Province. These geologic changes influenced distribution and diversification of Cutthroat Trout <em>Oncorhynchus clarkii</em> and allowed connections between Snake River, Colorado River, and Great Basin fish populations beginning in the late Miocene. Studies of detrital zircon grains in Miocene to Holocene fluvial sands of the Snake River document the eastward migration of the regional drainage divide from central Idaho to northwestern Wyoming. This migration was concomitant with the southwest migration of the North American tectonic plate over the YSRP hotspot. In the late Miocene and Pliocene, since 10 million years before present (Ma), the Chalk Hills and Glenns Ferry lake systems formed on the western Snake River Plain and were hosts to diverse fish fauna. The modern Snake River formed after 3 Ma with the cutting of Hells Canyon and integration of the Snake and Columbia River drainage. In the Great Basin south of the Snake River watershed, Lake Lahontan has a history that goes back to the Miocene. Connections between the western Snake River Plain and the Great Basin were recurrent over the past 10 myr. In southeastern Idaho, the Bear River has had a complex drainage interaction with the Snake River and Bonneville watersheds. Lake Bonneville, in northern Utah, grew during Pleistocene glacial climate regimes. The modern Bear River connection to Lake Bonneville was initiated about 50,000 years before the present. The integration of the Green River with the Colorado River occurred in the late Miocene, developing after breaking of Eocene connections between the Green River and streams draining to the Atlantic Ocean. In sum, geological constraints are compatible with patterns of fish fossils and genetic linkages and identify mechanisms of colonization and isolation of fish populations that have resulted in regional diversification of Cutthroat Trout.

The South Platte River Basin, Colorado

2020 ◽  
pp. 35-44
Author(s):  
Douglas A. Greenley ◽  
Richard G. Walsh ◽  
Robert A. Young
Keyword(s):  
River Basin ◽  
The South ◽  
Platte River ◽  
South Platte River ◽  
South Platte ◽  
Platte River Basin ◽  
South Platte River Basin

scholarly journals Climate-driven disturbances in the San Juan River sub-basin of the Colorado River

2018 ◽  
Vol 22 (1) ◽  
pp. 709-725 ◽  
Author(s):  
Katrina E. Bennett ◽  
Theodore J. Bohn ◽  
Kurt Solander ◽  
Nathan G. McDowell ◽  
Chonggang Xu ◽  
...  
Keyword(s):  
Climate Change ◽  
Water Resources ◽  
Land Cover ◽  
River Basin ◽  
Colorado River ◽  
Hydrologic Model ◽  
San Juan ◽  
Forest Disturbances ◽  
San Juan River ◽  
The Impact

Abstract. Accelerated climate change and associated forest disturbances in the southwestern USA are anticipated to have substantial impacts on regional water resources. Few studies have quantified the impact of both climate change and land cover disturbances on water balances on the basin scale, and none on the regional scale. In this work, we evaluate the impacts of forest disturbances and climate change on a headwater basin to the Colorado River, the San Juan River watershed, using a robustly calibrated (Nash–Sutcliffe efficiency 0.76) hydrologic model run with updated formulations that improve estimates of evapotranspiration for semi-arid regions. Our results show that future disturbances will have a substantial impact on streamflow with implications for water resource management. Our findings are in contradiction with conventional thinking that forest disturbances reduce evapotranspiration and increase streamflow. In this study, annual average regional streamflow under the coupled climate–disturbance scenarios is at least 6–11 % lower than those scenarios accounting for climate change alone; for forested zones of the San Juan River basin, streamflow is 15–21 % lower. The monthly signals of altered streamflow point to an emergent streamflow pattern related to changes in forests of the disturbed systems. Exacerbated reductions of mean and low flows under disturbance scenarios indicate a high risk of low water availability for forested headwater systems of the Colorado River basin. These findings also indicate that explicit representation of land cover disturbances is required in modeling efforts that consider the impact of climate change on water resources.

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