Describing Species Status of Rhinichthys osculus, the Santa Ana Speckled Dace, Among the Watersheds of Southern California Using Nuclear DNA Introns

RM 218

Rhinichthys osculus, the Speckled Dace, is the most widely distributed freshwater fish in the Western United States. It inhabits small flowing streams and springs. While at one time this species was found in countless numbers in many California watersheds, its populations have been greatly reduced due to environmental and ecological factors. Locally, R. osculus, known as the Santa Ana Speckled Dace, can be found in the Santa Ana Watershed drainages, with its nearest neighbor populations inhabiting the Colorado River, Owens Valley, and Central Coast inland waters. While mitochondrial DNA is an effective introductory look at the characterization of these varying populations, a more definitive view requires genetic information gathered from the sequencing of nuclear DNA markers. Specifically, within nuclear DNA, there exist segments called introns, which do not code for the expression of proteins. Due to this fact, they are less subject to the effects of natural selection and therefore are highly conserved regions among the species while also being highly variable between populations. By utilizing the genetic sequencing differences between populations we can show the Santa Ana Dace to be a “distinct population segment” among those throughout the most southwestern United States region.