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rivers are moderately to highly divergent from the Colorado River subbasin and they are highly to greatly diverged from the Dolores River subbasin. The San Juan subbasin shows high to great divergence from the other systems, with the exception of two sites (26 and 27) which show moderate divergence from the Yampa and White river subbasins. The Fst values indicate that each major river system contains its own unique assemblage of speckled dace. Variation within those river systems exists but generally cannot be shown to be significant, either due to sample size or lack of strong divergence. In addition to the Fst indices, we generated Nm values (Table 7). These are estimates of the number of migrants between pairs of populations per generation. They are a function of the Fst values in Table 6 and generally high numbers of migrants are predicted within major drainages and low numbers between drainages. Proper interpretation of these projections requires consideration of a historical component (or phylogenetic signal) that is ignored in F statistics. That is, individuals can be identical or similar by descent rather than identical because of recent migration events. Assume that genetically homogeneous ancestral fish initially entered all of the river systems. Over time, some of the individuals in the new populations would begin to diverge, but others could still retain the ancestral genotype. This would, on a population genetic time scale (ie. recent), be interpreted as evidence of migration when in fact no migration may have occurred in the past thousand or more years. For example, only unique speckled dace haplotypes are found in the San Juan subbasin (Table 5), but both the Fst and Nm values (Tables 6 and 7) suggest ongoing genetic interchange between the San Juan and Yampa rivers. We therefore recommend caution in viewing the Fst and Nm values alone to interpret the degree of uniqueness of populations. The analysis of molecular variance (Table 8) shows that most of the variability occurs within populations (81.63%). This result was anticipated in the review of Table 5. Most of the remaining variability occurred between the different river subbasins (17.89%). Within river subbasin variation was less than 1 %. The fixation indices also show this same result, where Fsc, the F statistic between populations and groups by river subbasin (c), was 0.0058 while both Fst and Fct had much higher index values. The values for both Fst and Fct were highly significant while that for Fsc was not significant. This again indicates that strong within population genetic structuring exists as well as differences between the major river systems, but little genetic variation exists among populations within the river subbasins. A visual representation of the major haplotypes in each population (Figure 2) shows how the haplotypes are distributed among populations. The Gunnison site is not included because only unique haplotypes were found in that system. The dominant speckled dace haplotype, designated as haplotype A (Table 9, also haplotype I Table 5), is found throughout all drainages except the San Juan. This haplotype is most abundant in the Dolores and Colorado River subbasins, but occurs sporadically in lower frequencies in both the White and Yampa rivers. Although not the most abundant form in the Little Snake River, haplotype 0 (haplotype 78), appears to be the dominant pattern in the Yampa subbasin. Haplotype I dominates the White River subbasin and, as noted above, haplotype A dominates the Colorado and Dolores subbasins. Haplotype D tends to be a second abundant pattern in the Dolores River, but it was also found at site 13 (Rifle Creek) in the Colorado River subbasin. The San Juan subbasin is dominated by haplotypes E and F. The assorting of various abundant haplotypes by subbasins indicates that while some gene flow may be occurring, within subbasin movement of fish is more likely. 31