Evolution
Since the end of the last glaciation (about 12,000 years ago), whitefish have re-colonized many North American lakes, from different directions, from refugia that represent genetically diverged stocks or races. After the invasions, the whitefish have also diversified into different populations locally, such that now in many lakes two main ecotypes are recognized within the species: a normal and a dwarf ecotype. These normal and dwarf ecotypes are mainly differentiated by the benthic and pelagic zone they occupy, respectively. Normal whitefish also grow much bigger and live much longer than the dwarf ecotype.
Many of these populations live in sympatry, yet are reproductively isolated. The fact that they are young species makes them prime candidate to study the evolutionary forces driving their ecological divergence and reproductive isolation.
Read more about this topic: Lake Whitefish
Famous quotes containing the word evolution:
“As a natural process, of the same character as the development of a tree from its seed, or of a fowl from its egg, evolution excludes creation and all other kinds of supernatural intervention.”
—Thomas Henry Huxley (1825–95)
“Analyze theory-building how we will, we all must start in the middle. Our conceptual firsts are middle-sized, middle-distanced objects, and our introduction to them and to everything comes midway in the cultural evolution of the race.”
—Willard Van Orman Quine (b. 1908)
“Historians will have to face the fact that natural selection determined the evolution of cultures in the same manner as it did that of species.”
—Konrad Lorenz (1903–1989)