Jared Tadje and Professor R. Paul Evans, Zoology
Geologic evidence indicates that there was a volcano about 30,000 years ago in Southern Idaho. Before the volcano, Bear Lake was connected to the Snake River, but lava flow from this volcano separated them. Currently, a river connects Bear Lake to the Lake Bonneville region surrounding the Great Salt Lake (Fig. 1). Many people believe that the Bear Lake cutthroat trout evolved from other cutthroat subspecies in the Lake Bonneville Region. My hypothesis is that they are more closely related to the cutthroat subspecies in the Snake River system, and that they evolved together before the volcano separated them. I studied the relationships between cutthroat subspecies in the Snake River (Yellowstone cutthroat), Bear Lake, and Lake Bonneville region to provide evidence for or against this hypothesis.
I amplified sections of mitochondrial DNA from these fish using the Polymerase Chain Reaction, cut them with restriction enzymes, and performed gel electrophoresis. This procedure creates unique banding patterns for each population, and allowed me to characterize each population according to haplotype. I studied the CytB, ND1, and ND2 regions of the mitochondrial DNA, using the following eight restriction enzymes for each region: AluI, CfoI, DdeI, HaeIII, HinfI, MboI, MspI, and RsaI. Using three regions and eight restriction enzymes allows for 24 different areas of variation, thus increasing the possibility of finding differences.
The CytB region is more conserved than the ND1 and the ND2 regions of the mitochondrial DNA. Because of this, a difference in the CytB region of two individuals signifies a very distant relationship. Therefore, the CytB region was most useful in differentiating between Yellowstone cutthroat and Bonneville cutthroat. Of the eight restriction enzymes used, MboI and HaeIII were the most useful in this analysis. Cutthroat trout from Bear Lake and Sugar Pine Creek (a tributary to Bear Lake) were tested and compared to individuals from Yellowstone and Bonneville. From Bear Lake, all ten individuals tested with MboI and HaeIII in the CytB region displayed the Yellowstone haplotype. Of nine individuals tested from Sugar Pine Creek, eight displayed the Yellowstone haplotype and one displayed the Bonneville haplotype (Fig. 2).
Preliminary data is consistent with Bear Lake cutthroat being most similar to the Yellowstone cutthroat. It is impossible to tell from this data if cutthroat trout initially inhabited Bear Lake and then spread into surrounding regions, or vice versa. However, evidence is consistent with the hypothesis that these two populations were once connected. As previously mentioned, the CytB region helps to establish coarse relationships. By examining more populations and using more restriction enzymes, it is possible to “fine tune” these relationships. I will continue this study by examining fish from selected regions surrounding Bear Lake. The data obtained will describe the relationship between the cutthroat trout in the Bonneville, Yellowstone, and Bear Lake regions in more detail.
