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Gary W. Dickson, et al. 
Fig. 1. Allele frequency distributions for phosphoglucose isomerase and phospho- 
glucomutase in the study area. Insert shows location of the six caves sampled for Crangonyx 
antennatus in relation to the major surface drainage in the Powell Valley, Lee County, 
Virginia. 1. Roadside No. 1 Cave (RD), 2. Molly Wagle Cave (MW), 3. Sweet Potato Cave 
(SP), 4. Cope Cave (C), 5. Spangler Cave (S), and 6. Gallohan No. 2 Cave (G). 
whether electromorphs produced at the same locus in different popula- 
tions were identical or different, amphipods from all six populations were 
run on the same gels. 
RESULTS 
All population samples were monomorphic for the same electromorph 
at six loci (G-6-P, IPO, AO, MDH, GP-1 and GP-2). Electromorph fre- 
quencies for the two polymorphic loci are given in Table 1. A total of five 
allelic products were distinguished for both PGI and PGM, although in 
only one case (PGM, Molly Wagle Cave) were all five electromorphs ob- 
served in a single cave. For eight loci in C. antennatus , polymorphism 
(proportion of loci polymorphic) equals 0.25. The mean proportion of loci 
