Great Bear Lake is the most northerly lake of its size (i.e., 32 000 km2) and sustains unusually high diversity within species, providing unique opportunities to study incipient stage of speciation. However, the extent and mechanisms of diversification within a species in large northern lakes remain unknown. In contrast to other large lakes, the pristine environment of Great Bear Lake should facilitate my investigation of divergence in a natural setting. I will compare and contrast patterns of divergence in Lake Trout (4 forms), Cisco (2-4 forms), and Lake Whitefish (4 forms) observed in Great Bear Lake to determine if common mechanisms are driving differentiation across species. Understanding variation within and among species within this freshwater system should help identify processes that can modify interactions among species, ultimately affecting species-specific evolutionary trajectories. Multiple forms within a species contributes substantially to the biodiversity in northern systems and has been associated with ecosystem resilience to disturbances (e.g., climate change), highlighting the importance of understanding the foundation of biological diversity.