|Abstract or Summary
- Speckled dace (Rhinichthys osculus) is a small cyprinid that is geographically widespread throughout western North America, and the most frequently occurring sh in Oregon. Because of the genetic and morphological variation in this species across its range, it has been referred to as a "species complex" and no revision to its taxonomy has occurred since 1984. We investigated the phylogenetics, population genetics, and morphometrics of speckled dace from Oregon's Great Basin region to describe the genetic and morphological variation of speckled dace, identify any unrecognized taxonomic diversity, and to test the validity of Foskett Spring speckled dace, an undescribed putative subspecies that occurs in a single spring within Warner Valley in Southeast Oregon. We collected morphometric and genetic data from Foskett Spring and the surrounding basins (Warner, Goose Lake, Lake Abert, Silver Lake, and Malheur), as well as Stinking Lake Spring (located within Malheur). We created Maximum Likelihood and Bayesian phylogenetic trees from mitochondrial ND2 and nuclear S7 sequence data and genotyped eight microsatellite loci. We identi fied three genetic clades within our samples area that warrant species-level status: Malheur stream dace, Stinking Lake Spring dace, and dace from the other four basins. Population structure was detected at the basin-level and separated Foskett Spring dace from other dace in Warner Valley. The geometric and linear morphometric data indicate that overall body shape did not di ffer among sh occupying streams in these basins, except for in Warner Valley dace, which had larger heads. The two populations of spring dace were distinct from stream dace by having more posterior dorsal fins, and were distinct from each other in head size. With this data we recommend species status for Malheur stream dace, Stinking Lake Spring dace, and dace from the other basins. Because of the strong morphological and slight genetic distinction of Foskett Spring speckled dace, ESU status is recommended, and this population will likely continue to be protected under the ESA.