Three other prezygotic barriers are behavioral isolation, mechanical isolation, and gametic isolation. In behavioral isolation, reproduction between similar species is prevented because each group possesses its own characteristic courtship behaviors. Wood and leopard frogs exhibit behavioral isolation because the males of each species have vocalizations that only attract females of their species.

Mechanical isolation occurs because the genital organs of different species are incompatible. Even if members of two species court and attempt copulation, mating is not successful. In plants, mechanical isolation often occurs in flowering plants pollinated by insects. The flowers of black sage and white sage are structurally different and are pollinated by different species of insects. In this example, each insect species pollinates flowers of only one of the sage species. Therefore, interbreeding does not occur.

If the gametes of two species meet, fertilization may not occur because of gametic isolation, in which the egg and sperm of different species are incompatible. Gametic isolation is particularly important in aquatic environments because many aquatic animals release their gametes into the water, where fertilization takes place.