Cutthroat Trout: Evolutionary Biology and Taxonomy

2018 ◽  
Keyword(s):  
Evolutionary Biology ◽  
Cutthroat Trout ◽  
Westslope Cutthroat Trout ◽  
Oncorhynchus Clarkii ◽  
Coastal Cutthroat Trout ◽  
Lahontan Cutthroat Trout ◽  
Museum Samples ◽  
Yellowstone Cutthroat Trout ◽  
The 1960S

<em>Abstract</em>.—There has been considerable interest in the systematics and classification of Cutthroat Trout since the 1800s. Cutthroat Trout native to western North America (currently classified as <em>Oncorhynchus clarkii</em>) have historically been grouped or separated using many different classification schemes. Since the 1960s, Robert Behnke has been a leader in these efforts. Introductions of nonnative trout (other forms of Cutthroat Trout, and Rainbow Trout <em>O. mykiss</em>) have obscured some historical patterns of distribution and differentiation. Morphological and meristic analyses have often grouped the various forms of Cutthroat Trout together based on the shared presence of the “cutthroat mark,” high scale counts along the lateral line, and the presence of basibranchial teeth. Spotting patterns and counts of gill rakers and pyloric caeca have in some cases been helpful in differentiation of groups (e.g., Coastal Cutthroat Trout <em>O. c. clarkii</em>, Lahontan Cutthroat Trout <em>O. c. henshawi</em>, and Westslope Cutthroat Trout <em>O. c. lewisi</em>) currently classified as subspecies. The historical genetic methods of allozyme genotyping through protein electrophoresis and chromosome analyses were often helpful in differentiating the various subspecies of Cutthroat Trout. Allozyme genotyping allowed four major groups to be readily recognized (Coastal Cutthroat Trout, Westslope Cutthroat Trout, the Lahontan Cutthroat Trout subspecies complex, and Yellowstone Cutthroat Trout <em>O. c. bouvieri </em>subspecies complex) while chromosome analyses showed similarity between the Lahontan and Yellowstone Cutthroat trout subspecies complex trout (possibly reflecting shared ancestral type) and differentiated the Coastal and Westslope Cutthroat trouts from each other and those two groups. DNA results may yield higher resolution of evolutionary relationships of Cutthroat Trout and allow incorporation of ancient museum samples. Accurate resolution of taxonomic differences among various Cutthroat Trout lineages, and hybridization assessments, requires several approaches and will aid in conservation of these charismatic and increasingly rare native fishes.

Cutthroat Trout: Evolutionary Biology and Taxonomy

2018 ◽  
Author(s):  
Joseph P. Brunelli
Keyword(s):  
Evolutionary Biology ◽  
Cutthroat Trout ◽  
Paternal Inheritance ◽  
Westslope Cutthroat Trout ◽  
Chromosome Marker ◽  
Mitochondrial Markers ◽  
Coastal Cutthroat Trout ◽  
Lahontan Cutthroat Trout ◽  
Yellowstone Cutthroat Trout

<em>Abstract</em>.—A Y chromosome marker shared with Rainbow Trout <em>Oncorhynchus mykiss </em>has been sequenced in many Cutthroat Trout <em>O. clarkii </em>subspecies. The marker is found in and inherited through males. It evolves more slowly than the maternally inherited mitochondrial DNA. The marker delineates the four major groups of Cutthroat Trout: the Lahontan Cutthroat Trout <em>O. c. henshawi </em>subspecies complex, the Yellowstone Cutthroat Trout <em>O. c. bouvieri</em> subspecies complex, Westslope Cutthroat Trout <em>O. c. lewisi</em>, and Coastal Cutthroat Trout <em>O. c. clarkii</em>. The paternal inheritance pattern of the Y marker makes it useful for dissecting the origins of fish with mixed ancestries. We describe a case study using both Y and mitochondrial markers in Lahontan Cutthroat Trout subspecies complex trout populations. Our results confirmed Lahontan Cutthroat Trout affinities for the Paiute Cutthroat Trout <em>O. c. seleniris</em> and Willow–Whitehorse Creek Cutthroat Trout. However, we found evidence of a complex ancestry for Guano Creek, Oregon trout, a group that has been proposed by some to be related to the Alvord Cutthroat Trout, a subspecies thought to be extinct.

Cutthroat Trout: Evolutionary Biology and Taxonomy

2018 ◽  
Keyword(s):  
Evolutionary Biology ◽  
Cutthroat Trout ◽  
River Basins ◽  
Lake Basin ◽  
Evolutionarily Significant Unit ◽  
Oncorhynchus Clarkii ◽  
Northern Nevada ◽  
Lahontan Cutthroat Trout ◽  
Carson River ◽  
Evolutionary Units

<em>Abstract</em>.—Lahontan Cutthroat Trout (LCT) <em>Oncorhynchus clarkii henshawi </em>and Paiute Cutthroat Trout (PCT) <em>O. c. selernis </em>are found in the Lahontan hydrographic basin of northern Nevada, northeastern California, and southeastern Oregon and together form the Lahontan Basin evolutionary lineage of Cutthroat Trout <em>O. clarkii</em>. The Alvord Cutthroat Trout <em>O. c. </em>ssp. native to the Alvord Lake subbasin in the northwestern Lahontan Basin was also part of this lineage but went extinct due to Rainbow Trout <em>O. mykiss </em>introgression in the mid-20th century. Both LCT and PCT are federally listed as threatened under the U.S. Endangered Species Act. Given its historic distribution in a single small stream and both phenotypic and genetic distinctiveness, PCT is currently recognized as a separate evolutionarily significant unit (ESU). For LCT, three ESUs are identified based upon meristic, morphological, ecological, and genetic data. These putative LCT ESUs separate lacustrine forms in the western Lahontan Basin (Truckee, Carson, and Walker River basins) from largely fluvial forms in the eastern Lahontan Basin (Humboldt and Reese River basins) and northwestern Lahontan Basin (Quinn River, Coyote Lake, and Summit Lake basins). The more recent recognition of a much longer evolutionary history of Cutthroat Trout and several influential genetic papers identifying previously unrecognized diversity within Cutthroat Trout have prompted a need to re-evaluate the overall taxonomy of this species. Here, we review earlier literature and draw on new information from recent studies to delineate uniquely identifiable evolutionary units within the Lahontan Basin lineage of Cutthroat Trout. Though in several cases various anthropogenic and natural influences have made definitive conclusions difficult, based on this collective information and the goal of conserving potentially important genetic, evolutionary, and life history diversity, we propose recognition of six uniquely identifiable evolutionary units within the Lahontan Cutthroat Trout lineage: (1) Paiute Cutthroat Trout—upper East Carson River; (2) western Lahontan Basin—Truckee, Walker, and Carson rivers together with Summit Lake; (3) northwestern Lahontan Basin—Quinn River; (4) eastern Lahontan Basin—Humboldt and Reese rivers; (5) Lake Alvord basin—Virgin-Thousand and Trout Creek drainages; and (6) Coyote Lake basin—Willow and Whitehorse rivers.

Cutthroat Trout: Evolutionary Biology and Taxonomy

2018 ◽  
Keyword(s):  
Evolutionary Biology ◽  
Colorado River ◽  
Species Concept ◽  
Cutthroat Trout ◽  
Rocky Mountain ◽  
Zoological Nomenclature ◽  
High Likelihood ◽  
Westslope Cutthroat Trout ◽  
Systematic Revision ◽  
Oncorhynchus Clarkii

<em>Abstract</em>.—The 2015 special workshop on the taxonomy and evolutionary biology of Cutthroat Trout highlighted the need for a modern systematic revision of Cutthroat Trout. Pending such a revision, the consensus of this panel was that Cutthroat Trout taxonomy should be based on the unified species concept. The current classification of Cutthroat Trout is based on Benhke’s “major and minor subspecies,” which is incompatible both with the unified species concept, which logically excludes subspecies, and the International Code for Zoological Nomenclature, which does not recognize major and minor subspecies. A compromise, interim classification is proposed, which captures Benhke’s ideas about Cutthroat Trout evolution and other recent information and retains trinomials for his “minor” subspecies, entities deserving re-evaluation in any subsequent systematic revision. Four species are recognized in this interim classification: Coastal Cutthroat Trout <em>Oncorhynchus clarkii</em>, Westslope Cutthroat Trout <em>O. lewisi</em>, Lahontan Cutthroat Trout <em>O. henshawi</em>, and Rocky Mountain Cutthroat Trout <em>O. virginalis</em>. The latter two contain recognized, named subspecies—<em>O. henshawi</em> with four (one extinct) and <em>O. virginalis</em> with seven (one extinct). Substantial nomenclatural problems are described, such that some common names are likely to be more stable than some scientific names until problems are resolved. Significant among these nomenclatural problems are the need to stabilize Rocky Mountain Cutthroat Trout <em>Salar virginalis</em> Girard with a neotype selection; the recognition of <em>Salmo stomias</em> Cope as a synonym of Rio Grande Cutthroat Trout <em>Salar virginalis</em> Girard and, consequently, the absence of a scientific name for Greenback Cutthroat Trout; the high likelihood that <em>Salmo bouvieri</em> Bendire is not a Yellowstone Cutthroat Trout; the high likelihood that the surviving syntype of <em>Salmo pleuriticus</em> Cope is a Westslope Cutthroat Trout and not a Colorado River Cutthroat Trout; and the related need to stabilize <em>S. pleuriticus</em> Cope, either with a lectotype designation from the surviving syntype, which might place <em>S. pleuriticus</em> Cope as a synonym of Westslope Cutthroat Trout, or, if it can be justified, a neotype designation using a Colorado River specimen.

Cutthroat Trout: Evolutionary Biology and Taxonomy

2018 ◽  
Keyword(s):  
Evolutionary Biology ◽  
Cutthroat Trout ◽  
River Basins ◽  
Nucleotide Polymorphisms ◽  
Westslope Cutthroat Trout ◽  
Glacial Cycles ◽  
Oncorhynchus Clarkii ◽  
Coeur D'alene ◽  
1 John ◽  
John Day

<em>Abstract</em>.—Identifying units of conservation of aquatic species is fundamental to informed natural resources science and management. We used a combination of mitochondrial and nuclear molecular methods to identify potential units of conservation of Westslope Cutthroat Trout <em>Oncorhynchus clarkii lewisi</em>, a taxon native to montane river basins of the northwestern United States and southwestern Canada. Mitogenomic sequencing identified two major lineages composed of nine monophyletic clades, and a well-supported subclade within one of these, largely delineated by river basins. Analyses of microsatellites and single nucleotide polymorphisms corroborated most of these groupings, sometimes with less resolution but demonstrating more complex connections among clades. The mitochondrial and nuclear analyses revealed that Pleistocene glacial cycles profoundly influenced the distribution and divergence of Westslope Cutthroat Trout, that this taxon crossed the Continental Divide in two separate events, and that genetically pure but nonindigenous fish were widely distributed. Herein, we recognize nine geographically discrete, cytonuclear lineages largely circumscribed by major river basins as potential units of conservation: (1) John Day; (2) Coeur d’Alene; (3) St. Joe; (4) North Fork Clearwater; (5) Salmon; (6) Clearwater headwaters; (7) Clearwater–eastern Cascades; (8) neoboreal, consisting of most of the Columbia upstream from central Washington, the Fraser in British Columbia, and the South Saskatchewan in Alberta; and (9) Missouri.

Cutthroat Trout: Evolutionary Biology and Taxonomy

2018 ◽  
Author(s):  
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Rainbow Trout ◽  
Evolutionary Biology ◽  
Isolation By Distance ◽  
Cutthroat Trout ◽  
Population Connectivity ◽  
Oncorhynchus Clarkii ◽  
Habitat Alterations ◽  
Coastal Cutthroat Trout

<em>Abstract</em>.—We examined patterns of dispersal and colonization after Cordilleran glaciations, population connectivity, levels of genetic diversity, and potential impacts of anthropogenic changes to Coastal Cutthroat Trout <em>Oncorhynchus clarkii clarkii</em>. Populations were mostly small with restricted dispersals but exchanged one to two migrants per generation on average. Genetic differences among local populations of Coastal Cutthroat Trout accounted for approximately three-fourths of the total genetic variation among groups, with differences among different geographical groups accounting for the rest. Because of this, hierarchical geographical population structure was difficult to detect except at small geographical scales that reflected local dispersal and gene flow or at broad geographical scales that reflected divergence associated with long-term isolation during Cordilleran glacial advances. Evolutionary processes such as gene flow and genetic drift reflected in isolation by distance occurred at distances up to 600–700 km but mostly lesser distances, whereas divergence associated with Pleistocene glaciation occurred at 1,900 km or greater. Glacial refugia existed south of the Salish Sea along the Washington, Oregon, and California coasts; in the Haida Gwaii or Alexander Archipelago; and possibly near the central coast of British Columbia near Bella Coola. Throughout the range, hybridization with Rainbow Trout <em>O. mykiss </em>or steelhead (anadromous Rainbow Trout) appears to occur naturally at low levels, but releases of hatchery-produced <em>O. mykiss </em>can lead to higher levels of hybridization and rarely hybrid swarms. Degraded habitat may contribute to hybridization, but most anthropogenic habitat alterations reduce habitat quantity and quality and disrupt opportunities for dispersal, contributing to declines in abundance, population connectivity, and genetic diversity.

Metabolic performance and thermal preference of Westslope Cutthroat Trout Oncorhynchus clarkii lewisi and non-native trout across an ecologically relevant range of temperatures

2021 ◽  
Author(s):  
Camille J. Macnaughton ◽  
Travis C. Durhack ◽  
Neil J. Mochnacz ◽  
Eva C. Enders
Keyword(s):  
Brook Trout ◽  
Cold Water ◽  
Cutthroat Trout ◽  
Intermittent Flow ◽  
Performance Curve ◽  
Westslope Cutthroat Trout ◽  
Oncorhynchus Clarkii ◽  
Thermal Niche ◽  
Preferred Temperatures ◽  
Metabolic Performance

The physiology and behaviour of fish are strongly affected by ambient water temperature. Physiological traits related to metabolism, such as aerobic scope (AS), can be measured across temperature gradients and the resulting performance curve reflects the thermal niche that fish can occupy. We measured AS of Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) at 5, 10, 15, 20, and 22°C and compared temperature preference (Tpref) of the species to non-native Brook Trout, Brown Trout, and Rainbow Trout. Intermittent-flow respirometry experiments demonstrated that metabolic performance of Westslope Cutthroat Trout was optimal at ~15 °C and decreased substantially beyond this temperature, until lethal temperatures at ~25 °C. Adjusted preferred temperatures across species (Tpref) were comparatively high, ranging from 17.8-19.9 °C, with the highest Tpref observed for Westslope Cutthroat Trout. Results suggest that although Westslope Cutthroat Trout is considered a cold-water species, they do not prefer or perform as well in cold water (≤ 10°C), thus, can occupy a warmer thermal niche than previously thought. The metabolic performance curve (AS) can be used to develop species‐specific thermal criteria to delineate important thermal habitats and guide conservation and recovery actions for Westslope Cutthroat Trout.

scholarly journals Hybridization of Snake River Cutthroat in the Lower Gros Ventre River

2006 ◽  
Vol 30 ◽  
pp. 110-113
Author(s):  
Ryan Kovach ◽  
Lisa Eby
Keyword(s):  
Exotic Species ◽  
National Park ◽  
Cutthroat Trout ◽  
Snake River ◽  
Oncorhynchus Clarki ◽  
Oncorhynchus Clarkii ◽  
Grand Teton National Park ◽  
Water Diversions ◽  
Yellowstone Cutthroat Trout ◽  
Special Concern

The cutthroat trout Oncorhynchus clarki is Wyoming's only native trout. The Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) is designated as a "species of special concern" by a number of agencies and conservation groups. Although the Yellowstone cutthroat trout has recently avoided federal listing because of robust headwater populations (USFWS 2006), they face continued threats across their range. The fine-spotted Snake River native trout is a morphologically divergent ecotype of the Yellowstone subspecies, although it is not genetically distinguishable (Allendorf and Leary 1988, Novak et al. 2005). The Gros Ventre, an important tributary of the Snake River located partially in Grand Teton National Park, historically supported robust populations of fine­ spotted Snake River cutthroat trout. Principal threats to Gros Ventre native trout, especially in the lower end of the drainage within the park boundaries, include both water diversions (loss of water and fish into irrigation ditches) and presence of exotic species.

The interactive effects of stream temperature, stream size, and non-native species on Yellowstone cutthroat trout

2021 ◽  
Author(s):  
Robert Al-Chokhachy ◽  
Mike Lien ◽  
Bradley B. Shepard ◽  
Brett High
Keyword(s):  
Native Species ◽  
Cutthroat Trout ◽  
Population Level ◽  
Stream Temperature ◽  
Interactive Effects ◽  
Oncorhynchus Clarkii ◽  
Wide Range ◽  
Yellowstone Cutthroat Trout ◽  
Stream Size ◽  
Native Salmonids

Climate change and non-native species are considered two of the biggest threats to native salmonids in North America. We evaluated how non-native salmonids and stream temperature and discharge were associated with Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) distribution, abundance, and body size, to gain a more complete understanding of the existing threats to native populations. Allopatric Yellowstone cutthroat trout were distributed across a wide range of average August temperatures (3.2 to 17.7ºC), but occurrence significantly declined at colder temperatures (<10 ºC) with increasing numbers of non-natives. At warmer temperatures occurrence remained high, despite sympatry with non-natives. Yellowstone cutthroat trout relative abundance was significantly reduced with increasing abundance of non-natives, with the greatest impacts at colder temperatures. Body sizes of large Yellowstone cutthroat trout (90th percentile) significantly increased with warming temperatures and larger stream size, highlighting the importance of access to these more productive stream segments. Considering multiple population-level attributes demonstrates the complexities of how native salmonids (such as Yellowstone cutthroat trout) are likely to be affected by shifting climates.

Cutthroat Trout: Evolutionary Biology and Taxonomy

2018 ◽  
Keyword(s):  
Rainbow Trout ◽  
Rocky Mountains ◽  
Evolutionary Biology ◽  
Cutthroat Trout ◽  
Taxonomic Revision ◽  
River Basins ◽  
Evidence Based ◽  
Oncorhynchus Clarkii ◽  
Southern Rocky Mountains ◽  
Green Lineage

<em>Abstract</em>.—One objective of systematics is to recognize species in a manner that minimizes the disparity between species as real entities in nature and species as a Linnaean category. Reconciliation requires a conceptualization of species consistent with evolutionary processes that yields predictive delimitation criteria. Here we review the unified species concept (USC) and its associated delimitation criteria as a prelude to revising the taxonomy of Cutthroat Trout <em>Oncorhynchus clarkii</em>. Additionally, in the context of the conceptualizing species as a separately evolving metapopulation, we briefly review how climate change may have influenced the connectivity and isolation of Cutthroat Trout within and among river basins, with a focus mainly on the Cutthroat Trout of the Southern Rocky Mountains. We summarize evidence based on delimitation criteria that distinguishes Rainbow Trout <em>O. mykiss</em> and Cutthroat Trout, Gila Trout<em> O. gilae </em>and Rainbow Trout, and blue lineage and green lineage Cutthroat Trout from the Southern Rocky Mountains. We advocate adopting the USC as a guide for taxonomic revision of Cutthroat Trout, recommend eliminating subspecies as a valid taxonomic designation, and expect—based on our evaluation of three pairs of species—that the taxonomy of Cutthroat Trout will be revised in ways that elevate some recognized subspecies to species status.

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