Intralacustrine Speciation of Salvelinus namaycush in Lake Superior: An Investigation of Genetic and Morphological Variation and Evolution of Lake Trout in the Laurentian Great Lakes

摘要

The lake trout (Salvelinus Namaycush) is a ubiquitous top-level predator of deep freshwater lakes and rivers in the northern U.S. and Canada. In Lake Superior, morphological and possible genetic differentiation has resulted in at least three recognizable forms of lake trout. The three different morphological forms have been thought to be the result of environmental adaptation to different depths. The most Widely recognized form is the 'lean', which inhabits the inshore lacustrine area of deep lakes less than 70 meters deep. A second for, the 'siscowet', is a robust lake trout which inhabits the deep basins of Lake Superior, at depth of 50 to over 150 meters. A third form is called the 'humper', or 'paperbelly', and lives over isolated shoals about 50 meters deep surrounded by water greater than 100 meters deep. Previous investigations of physiological difference amoung leans, sisowets, and humpers shoued that the phenotypic difference were heritable. Biogeographic changes since the Pleistocene glaciation had significant implications for divergence in life history adaptations amoung lake trout phenotypes. The possibility exists that these populations are undergoing speciation even though they are not separated by geographical barriers. the morphologically divergent population of lake trout in Lake Superior offer a unique opportunity to investigate and test the intralacustrin speciation hypotheis in Salvelinus namaycush.