A species is defined as organisms capable of interbreeding and producing fertile offspring. Diane Dodd examined the idea of speciation in fruit flies. She took fruit flies from a single population and divided them into separate populations living in different cages, each receiving different food sources. One group was given maltose-based foods and the other, starch-based foods. After many generations, the flies were tested to see which flies they preferred to mate with. Dodd found that "maltose flies" preferred other "maltose flies.” In this case, what lead to speciation?

Because the fruit flies were separated and given different food sources, the reproductive isolation came from habitat isolation. Temporal isolation occurs when different species reproduce at different times. Gametic isolation occurs when egg and sperm from two different species cannot combine in fertilization. Behavioral isolation occurs when two species have different courtship behaviors or mate preferences and thus find each other "unattractive".