westslope cutthroat trout from which we have comparable data 

 (Fig.l). Thus, it appears that on the average the Bitterroot 

 drainage populations appear to be genetically more variable than 

 populations of westslope cutthroat from other areas of Montana; 

 e.g. Lower Clark Fork around Noxon Reservoir, Hungry Horse region 

 of the South Fork Flathead, North Fork Flathead, and Upper 

 Missouri. 



We detected evidence of rainbow, westslope cutthroat, and 

 Yellowstone cutthroat trout genetic material at those loci that 

 differentiate these fishes in the Rattlesnake Creek sample (Table 

 4). This sample, therefore, came from an introgressed 

 population of westslope cutthroat, Yellowstone cutthroat, and 

 rainbow trout. When genetic material from all of these fishes is 

 present in one population, we can only obtain 'ballpark' 

 estimates of the proportional contribution of each taxa to the 

 population because many alleles at the diagnostic loci cannot 

 unambiguously be assigned to a particular taxon. For example, 

 the Gpi3(100) allele is characteristic of both rainbow and 

 Yellowstone cutthroat trout. We can state, however, that the 

 vast majority of the genetic material in this population is of 

 westslope cutthroat trout origin as the average frequency of the 

 five alleles that we can assign to this fish (Aatl(200), 

 Gpi3(92), Idh3(86), Mel(88), and Sdh(40)) in the sample is 0.941. 



Sincerely, 



' j2cJA^ d^LM.j'^ 



Robb Leary 



RL/pkf 

 Enclosures 



