High Levels of Genetic and Morphological Diversity Indicate Multiple Independent Lineages of Speckled Daces (Rhinichthys osculus) in the Streams and Springs of Oregon's Great Basin

The speckled dace (Rhinichthys osculus) is the most widespread native freshwater fish in western North America, and has diversified morphologically and genetically in streams and springs throughout its range. We used molecular phylogenetics, morphometrics and meristics to characterize that diversity throughout Oregon’s Great Basin, identify independently evolving lineages within the present concept of R. osculus, and test whether isolation in desert springs drives convergent morphological divergence away from the stream phenotype.  At least three and as many as seven isolated lineages within R. osculus might represent unrecognized species, several of which differ statistically in morphology as well as genetics. Two of these lineages appear to be confined to desert springs.  While spring fishes generally differ morphologically from their stream-dwelling relatives, we did not detect a universal spring phenotype. Rather, spring lineages diverge from their stream-dwelling relatives on different morphological axes, suggesting that the physical characteristics of each particular spring play a significant role in determining the morphology of the animals that inhabit it.  These results reveal unrecognized components of the biodiversity and evolutionary history of one of the most ubiquitous fishes in the American West.