Multiples Instances of Parallel Incipient Sympatric Speciation in Lake Charr Salvelinus Namaycush - Rapid Evolution in a Slow-Living Species

Studies that target newly diverging populations are key to understanding the importance of plasticity-related genes that mediate an organism's environmental responsiveness. Lake charr Salvelinus namaycush across North America represent young populations in the early stages of divergence and exhibit multiple morphologies of shallow and deep water ecotypes. The phenotypic distinctiveness of ecotype morphologies suggest that morphological differences are under some form of genetic control and have evolved some degree of reproductive isolation. In this study, we test the hypotheses that lake charr ecotypes are reproductively isolated and arose via parallel ecological sympatric speciation. We sampled tissue from ecotypes within four large lakes, Great Bear Lake, Great Slave Lake, Lake Mistassini and Lake Superior, and one small lake, Rush Lake. Results from mitochondrial and microsatellite DNA analyses, including a detailed case study within Rush Lake, suggest that ecotypes arose independently in lakes after colonization and that morphologically and ecologically differentiated lake charr ecotypes within lakes are largely indistinguishable genetically using neutral markers. This may be a consequence of phenotypic differences being linked to divergence at (non-neutral) genes or genomic regions associated with trophic morphology and life history, or that epigenetic processes dominate trophic phenotype at this stage in lake charr evolution.