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subbasins sampled in this study. To simplify the analysis we chose to only utilize the major haplotypes (Table9). Most of the minor haplotypes would be associated with the tips of the phylogenetic tree since they are usually locally derived patterns. The resulting phylogram (Figure 4) should be interpreted as giving general relationships among the major haplotypes. Running the entire set could potentially yield more resolution, but the general results are appropriate for our needs. The Gandy marsh population (western Utah) is basal to the speckled dace, followed by Virgin River speckled dace. Of the Colorado collections, Haplotype G from the San Juan, locations 26 and 27 (Figure 2), was marginally basal (bootstrap value of 51). At the next level a polytomy occurs where haplotypes C, E, F, G, and H are unresolved relative to the next clade. Three of these haplotypes, E, F, and H are unique to the San Juan River subbasin (Figure 2), and the remaining one, C, is unique to the Colorado River subbasin. While these haplotypes are unresolved, they are clearly basal to the remaining haplotypes (A, B, I-P), indicating that they are likely old patterns. The fact that the San Juan subbasin contains three of these basal forms indicates that it is phylogenetic ally unique relative to the other subbasins. The remaining clade (haplotypes A, B, I-P), which is also weakly supported by bootstrap values, does not contain San Juan River subbasin haplotypes, further evidence that the San Juan subbasin is unIque. The remaining clade (A, B, I-P) is also a polytomy, but it has some informative substructure. Haplotype B is a Colorado River subbasin pattern while haplotype A is a general pattern found in the Dolores, Yampa, White, and Colorado subbasins. Haplotypes D and N are mostly a Dolores -White River group, with N being found in only the White River subbasin and D being in the Dolores River and one location in the Colorado River subbasin. The remaining two clades, I, J, L, M and O,P, K, are White River-Yampa River haplotypes. While some of these are shared between the two subbasins, J and L are only found in the White River subbasin and 0 and P are only found in the Yampa River subbasin. This indicates that the Yampa and White River forms are closely related, yet both have distinct lines not found in the other. The Dolores and Colorado subbasins share haplotype A (as do the other parts of the Colorado River basin in Colorado with the exception of the San Juan subbasin), but haplotype D tends to be more frequent in the Dolores subbasin. Further separation of the Dolores relies on unique haplotypes which we did not include in the analysis. Haplotypes 16-26 (Table 5) are unique to the Dolores River subbasin. The phylogenetic analysis supports maintaining the various subbasins as distinct units. Speckled dace from one are not genetically the same as those from another subbasin. Speckled dace populations tend to be unique and speckled dace in different major river subbasins also tend to be significantly different from one another. Therefore maintenance of genetic diversity in this species should include recognition ofthe different evolutionary trajectories of the separate subbasins. Within these subbasins populations tend to share major haplotypes, thus the analysis of molecular variance showed no significant differences between populations within subbasins. However unique minor haplotypes do exist in different populations within subbasins (Figure 2) so as many populations should be preserved as possible to maintain their unique histories. 38