Reproductive Isolating Mechanisms

Date: 2015-10-07; view: 456.

A reproductive isolating mechanism is a structural, functional, or behavioral characteristic that prevents successful reproduction from occurring. These mechanisms divide into premating and postmating types.

Premating isolating mechanisms are anatomical or behavioral differences between two species that prevent the possibility of mating. Habitat isolation occurs when two species occupy different habitats, even within the same geographic range, so that they are less likely to meet and to attempt to reproduce. Temporal isolation occurs when two species live in the same location, but each reproduces at a different time of the year, preventing a successful mating. Behavioral isolation occurs when there are differences in mating behavior between two species. Mechanical isolation is the result of differences between two species in reproductive structures or other body parts, so that mating is prevented.

Postmating isolating mechanisms are the result of developmental or physiological differences between the members of two species after mating. Gamete isolation is the physical or chemical incompatibility of gametes of two different species. If the gametes lack receptors to facilitate fusion, they cannot form a zygote. An egg may have receptors only for the sperm of its own species. Zygote mortality is a mechanism that works when hybrids (offspring of parents of two different species) do not live to reproduce. Hybrid sterility occurs when the hybrid offspring are sterile (e.g., mules).