Mechanisms of Reproductive Isolation

Table 20.7 Mechanisms of Reproductive Isolation Prezygotic Mechanisms Behavioral isolation: Sexual behavior in different species are incompatible, or sexual attraction is lacking between them. Gametic isolation: Mating takes place between different species, but the gametes fail to unite with one another due to differences in gamete compatibility or to failure of male gametes to survive until fertilization of female gametes. Geographic isolation: Species reside in separate geographic locations or are separated by geographic features that prevent their contact. Habitat isolation: Species inhabit different ecosystems that prevent them from coming into contact. Mechanical isolation: Male and female genitalia or reproductive structures of different species are anatomically incompatible. Temporal isolation: Timing of reproductive ability or receptivity in different species is incompatible. Postzygotic Mechanisms Hybrid breakdown: Viable and fertile interspecies hybrids form, but after the F1 generation the fitness of the progeny of hybrids is less than that of progeny from nonhybrids. Hybrid inviability: The fertilized zygote of an interspecies mating fails to survive gestation. Hybrid sterility: Interspecies hybrids are viable but infertile.