Life History Variation Among Lake Trout Ecotypes: Linking Proximate and Ultimate Mechanisms

Sympatric char morphotypes or ecotypes have been thought to represent stages in species divergence.  Presumably these differing phenotypes are tightly associated with habitat preferences that may translate to differences in life histories.  Lake Superior is the only Laurentian Great Lake that contains self-sustaining populations of different lake trout ecotypes including the lean, siscowet, redfin and humper.  These ecotypes exhibit large differences in skeletal muscle lipid and morphometry that have been shown to have a genetic or epigenetic basis.  In addition, we have demonstrated that some of these ecotypes (leans and siscowets) are metabolically different, exhibit differing reproductive patterns (e.g. timing and skip spawning) and swimming behaviors within the water column.  These differences lead to interesting hypotheses related to life history strategies for energy storage and utilization, foraging, reproduction and even interactions with parasitic lampreys.  Hatchery reared lake trout ecotypes and their reciprocal crosses may provide the means to understand how these phenotypes lead to different life histories.