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:
“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)
“By contrast with history, evolution is an unconscious process. Another, and perhaps a better way of putting it would be to say that evolution is a natural process, history a human one.... Insofar as we treat man as a part of nature—for instance in a biological survey of evolution—we are precisely not treating him as a historical being. As a historically developing being, he is set over against nature, both as a knower and as a doer.”
—Owen Barfield (b. 1898)
“The evolution of humans can not only be seen as the grand total of their wars, it is also defined by the evolution of the human mind and the development of the human consciousness.”
—Friedrich Dürrenmatt (1921–1990)