An experiment demonstrating allopatric speciation in the fruit fly (Drosophila pseudoobscura) conducted by Diane Dodd. A single population of flies was divided into two, with one of the populations fed with starch-based food and the other with maltose-based food. After the populations had diverged over many generations, the groups were again mixed; it was observed that the flies continued to prefer mating with others from the same original population.