Diane Dodd's experiments using fruit flies demonstrated that
◦ formation of a reproductive barrier between two populations is more likely if they experience and adapt to different environmental conditions.
◦ the evolution of reproductive barriers occurs much too slowly to produce measurable effects in the laboratory.
◦ new species can form in a single generation by the production of new reproductive structures.
◦ reproductive barriers usually are absolute: Either two populations are fully willing and able to interbreed, or they are strictly separated by a fully effective reproductive barrier.