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DRAFT Willow Beach (Captive) Salt Camp Coyote Camp Boulders Willow Beach - Salt Camp 0.640 - Coyote Camp 0.164 0.443 - Boulders 0.163 0.113 0.553 - Table 4: Genetic differentiation among populations. Each table entry represents the proba- bility of the observed genotypic differences among population pairs given the null hypothesis of no underlying difference. Tests are based upon all six microsatellite loci. distribution, it is taken as evidence of significant differentiation. None of the comparisons among populations exhibited significant differentiation. Willow Beach (Captive) Salt Camp Coyote Camp Boulders Willow Beach - Salt Camp 0.000 - Coyote Camp 0.0053 0.0004 - Boulders 0.0223 0.0257 0.006 - Table 5: Proportion of total marker genetic variation, FST, occuring among population pairs. 3.8 Allelic differentiation An alternative approach to the comparisons descibed above is to focus on the difference in allele frequencies rather than genotype frequencies among populations. Diploid genotype frequencies can change every generation due to changes in mating structure. Allele frequen- cies should be more resistant to these changes. Allelic differentiation can be tested using a contingency table approach as above, but extensive theoretical work has been devoted to understanding those differences in the context of proportions of total allelic variation that occurs among populations (Wright; 1951; Nei; 1973; Weir and Cockerham; 1984). Table 5 summarizes the proportion of total allelic diversity that occurs among populations. With conspecific populations like the situation with Gila cypha, these numbers are linearly related to the time since isolation, though sampling and differences in effective size among popu- lations can cause this relationship to fail. This analyses presented here and in section 3.7 indicate that there is little differentiation among populations, either wild-sampled or captive. The one exception is that the Boulders site does seem to differ slightly, but not significantly from all the others. Again, this may be due primarily to the small sample size obtained from this site. It is important to note, however, that this differentiation also could represent a biologically meaningful situation such as a minor barrier to gene flow between Boulders and other wild populations; currently, there is not enough. genetic information to distinguish among these possibilities. The ecological data suggests the former rather than the latter. 0 7