The Cutthroat Trout Oncorhynchus clarkii has long been known to have four major genetic lineages, and these four lineages have now been elevated to the species level - the Cutthroat Trout has been split into four species: Coastal Cutthroat Trout O. clarkii; Lahontan Cutthroat Trout O. henshawi; Westslope Cutthroat Trout O. lewisi; and the Rocky Mountain Cutthroat Trout O. virginalis.
Every so often the American Fisheries Society publishes a volume titled "Common and Scientific Names of Fishes from the United States, Canada, and Mexico." The 8th Edition was published a few months ago. The publication is the output of the Committee on Names of Fishes, a joint committee of the American Fisheries Society and American Society of Ichthyologists and Herpetologists. This book is the authority for many on what is recognized as a species, of which many are continuously proposed in the scientific literature.
The elevation of the four Cutthroat Trout lineages to the species level follows the recommendations of Markle 2018. Markle 2018 was a chapter in a book titled "Cutthroat Trout: Evolutionary Biology and Taxonomy" published by the American Fisheries Society. The book was borne out of a 2015 workshop sponsored by the Western Division of the American Fisheries Society. A taxonomic revision of the Cutthroat Trout should be based on the Unified Species Concept, was one consensus of the workshop panel (see Queiroz 2007). Markle proposed an interim classification of the Cutthroat Trout complex, based on information presented in the workshop and published in the book. But there are still issues to resolve within each species.
So, there are now four Cutthroat Trout species. This is the iconic native trout of the western U.S, but several people I talked to recently were unaware of the change. What does this change mean? Maybe not much for the Coastal Cutthroat Trout and Westslope Cutthroat Trout that were each one subspecies under the old classification. But, the Paiute Cutthroat Trout is listed as a separate entity under the Endangered Species Act. So is the Lahontan Cutthroat Trout, of which the Paiute is a part (Uniquely Identifiable Ecological Unit? - see Peacock et al. chapter in the book). Will this change their listed status under ESA? What about the Rocky Mountain Cutthroat Trout? There are numerous recognized subspecies (under former Cutthroat Trout taxonomy) and lineages, some are rare (San Juan lineage). Will more proposals to list these entities be received? Most lineages are managed as unique entities already by the state agencies. Will anything change for management, or is it just a formal recognition of [the distinctness of] their evolutionary relationships?
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