Sympatric Polymorphism in Lake Trout in Great Bear Lake: Extensive Intra-Lake Morphological Diversification at Two Spatial Scales

Post-glacial lakes, common feature in northern landscapes provide favorable ecosystems for studying intra-specific diversity in fishes. Great Bear Lake with its large size and virtually pristine, recently colonized cold water habitats, provides unique opportunities for Lake Trout diversification. Previous work identified three common morphotypes in the shallow-water habitat of Great Bear Lake, displaying differences in head shape and fins and a fourth rarer group. The lack of body shape variation among groups combined with the size the lake, lead us to investigate geographic morphological patterns the five arms of Great Bear Lake. Genetic and morphological distance matrices were also compared to investigate potential parallel patterns, and suggested phenotypically plastic responses to distinct environments. Inter-arm morphological variation in body shape within morphotypes reveals another layer of diversity across this large and heterogeneous northern lake. Despite increasing attention to intraspecific polymorphism in post-glacial lakes, the extent of the potential for radiation remains unknown.