Genetic relationships of tui chub populations in the northwestern Great Basin and conservation implications for the Cow Head Tui Chub

The Cow Head Tui Chub, Siphateles thalassinus vaccaceps, is restricted to the small Cow Head basin in far northeastern California and northwestern Nevada. Using microsatellite DNA loci, we found extensive genetic variation among tui chub populations in the Cow Head and surrounding basins of the northwestern Great Basin. Our data support the systematic conclusions of earlier authors, while showing distinct intraspecific differences between populations in most subbasins within the pluvial basins examined. The Cow Head Tui Chub forms a distinctive population within S. thalassinus with greatest affinity to the tui chub in the Warner Valley into which the Cow Head Lake drains. Tui chubs from the Goose Lake and Pit River basins are genetically very similar. Warner, Abert, Summer Lake, Catlow and Guano basin tui chubs appear distinct, both from each other and from tui chubs in the other basins. However, genetic proximity and some overlap between populations in presumably isolated hydrologic basins (i.e. Summer–Goose–Warner) suggest the possibility of unrecognized hydrologic connections or anthropogenic transport across barriers. Current genetic diversity in the Cow Head Tui Chub population is similar to that of stream-associated populations. We suggest that the Cow Head Tui Chub should remain a species of conservation concern due to its highly restricted distribution in an arid environment. Successful conservation of this unique fish will depend on stewardship of its limited habitat and maintenance of connectivity between subpopulations in a manner that ensures its long-term viability.