A molecular taxonomy of Cottus in western North America

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Fishes of the genus Cottus –the sculpins—have long been a challenge for fish managers and ichthyologists in the West. They share streams, rivers, and lakes with trout and salmon, and depend on the same kinds of habitats with relatively cold, clean water. But because the morphological differences between species are subtle and seemingly geographically variable, it has been a challenge to catalog the diversity of species in western North America. To resolve this problem, we sought your help to build a regional collection of sculpin tissues, and used genetic sequences, species delimitation algorithms, and geography to delineate the number and distribution of species.

Thanks to contributions by over 130 biologists, academicians, students, and citizen scientists, we received over 8,300 specimens–representing every described species–from over 1,500 locations in every state and province across western North America to which sculpin were native. We sequenced 1–4 genes for one or more sculpins from every location (over 4,000 sculpins in all). We supplemented those data with sequences downloaded from public sequence libraries, which were georeferenced by using data in those libraries, consulting the publication with which the specimens were associated, or searching records of museums with substantial ichthyological collections. We also included specimens of two species from eastern North America, C. bairdii and C. cognatus, that were believed to be present in western North America, and the type species for the genus, C. gobio, from Europe.   Key findings: The current taxonomy recognizes 19 species from the region. We hypothesize that there are 37 species in 8 species complexes in western North America. These represent heretofore unrecognized species, previously recognized taxa resurrected from synonymy, and most of the currently recognized species. Nearly all species can be diagnosed with a single mitochondrial gene. Knowing where a specimen was collected is nearly as informative. A handful of currently recognized taxa showed little or no genetic differentiation from other species. We acknowledge that these taxa might be valid under other species concepts. Hybrids among sculpin are common, and some species are of ancient hybrid origin. Neither C. bairdii nor C. cognatus are found in western North America. We did propose, however, three new species within the former from eastern North America, and suspect that there may be others.

For further details, you can download the publication and supplemental materials describing this work from TreeSearch:  Young, Michael K.; Smith, Rebecca; Pilgrim, Kristine L.; Isaak, Daniel J.; McKelvey, Kevin S.; Parkes, Sharon; Egge, Jacob; Schwartz, Michael K. 2022. A molecular taxonomy of Cottus in western North America. Western North American Naturalist 82(2): 307-345. https://doi.org/10.3398/064.082.0208

Sculpin Qwest Presentations, Publications, and Posters

Lemoine, Michael; Young, Michael K.; McKelvey, Kevin S.; Eby, Lisa; Pilgrim, Kristine L.; Schwartz, Michael K. 2014. Cottus schitsuumsh, a new species of sculpin (Scorpaeniformes: Cottidae) in the Columbia River basin, Idaho-Montana, USA. Zootaxa. 3755(3): 241-258.

Young, Michael K.; McKelvey, Kevin S.; Pilgrim, Kristine L.; Schwartz, Michael K. 2013. DNA barcoding at riverscape scales: Assessing biodiversity among fishes of the genus Cottus (Teleostei) in northern Rocky Mountain streams. Molecular Ecology. doi: 10.1111/1755-0998.12091.

Nicholas B, Young M, Sidlauskas B. 2019. Genetic and morphological evidence suggests cryptic speciation within the Torrent Sculpin, Cottus rhotheus, across the Pacific Northwest. Annual meeting of the Oregon Chapter of the American Fisheries Society, Bend, OR, 7 March 2019.

Young M, Smith R, Pilgrim K, McKelvey K, Schwartz M, Isaak D, Parkes S, and the SculpinQwest Collaborative. 2019. A molecular reinterpretation of the biodiversity of Cottus in western North America. Annual meeting of the Washington-British Columbia Chapter of the American Fisheries Society, Bremerton, WA, 9 April 2019.

Young, Micahel K.; Isaak, Daniel J. 2014. Wanted: Your help to understand the diversity of Cottus in western North America. Poster.

Young, Michael K.; Smith, Rebecca; Pilgrim, Kristine L.; Isaak, Daniel J.; McKelvey, Kevin S.; Parkes, Sharon; Egge, Jacob; Schwartz, Michael K. 2022. A molecular taxonomy of Cottus in western North America. Western North American Naturalist 82(2): 307-345. https://doi.org/10.3398/064.082.0208.

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Other Links

• Climate-Aquatics Blog #30: Recording & Mapping Earth’s stream biodiversity from genetic samples of critters
  

• Climate-Aquatics Blog #53: DNA Barcoding & Fish Biodiversity Mapping

• The Aquatic eDNAtlas Project

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Sculpin Qwest Contact

Michael K. Young - Research Fisheries Biologist

USFS Rocky Mountain Research Station
Forestry Sciences Lab
800 East Beckwith Avenue
Missoula, MT 59801
Phone: 406-542-3254
michael.k.young@usda.gov