Drosophila pseudoobscura

Drosophila pseudoobscura is a species of fruit fly, used extensively in lab studies of the genetics of natural populations.
It was first used by Theodosius Dobzhansky and his colleagues. They collected samples from populations in western North America and Mexico, and grew them in 'population cages' in the laboratory. They were interested in natural selection, genetic drift, and other aspects of population genetics.
In 1989 Diane Dodd gave laboratory populations of "D. pseudoobscura" two different food types, starch and maltose. They rapidly evolved into two distinct groups after only eight generations with the different foods. As the two groups both showed a strong preference for mating with their own type, this was claimed as an example of speciation by reproductive isolation. Dodd's experiment has been repeated by others, and works with other kinds of fruit flies and foods.
In 2005, "D. pseudoobscura" was the second "Drosophila" species to have its genome sequenced, after "Drosophila melanogaster".