include factors that may contribute to the maintenance of genetic isolation.
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Speciation occurs when populations of organisms become reproductively isolated from each other. Two or more new sister species are said to have formed once they cannot interbreed with each other. Prezygotic isolating mechanisms (before mating), along with postzygotic isolating mechanisms(after fertilization) can all attribute to genetic isolation.
Prezygotic mechanisms (Factors which prevent individuals from mating)
Temporal isolation- Individuals do not mate because they are active at different times. This may be different times of the day or different seasons. The species mating periods may not match up. Individuals do not encounter one another during either their mating periods, or at all.
Ecological, or habitat isolation: Individuals only mate in their preferred habitat. They do not encounter individuals of other species with different ecological preferences.
Behavioral isolation: Individuals of different species may meet, but one does not recognize any sexual cues that may be given. An individual chooses a member of its own species in most cases.
Mechanical isolation: Copulation may be attempted but transfer of sperm does not take place. The individuals may be incompatible due to size or morphology.
Gametic incompatibility: Sperm transfer takes place, but the egg is not fertilized.
Postzygotic isolating mechanisms
Genomic incompatibility, hybrid inviability or sterility.
Zygotic mortality: The egg is fertilized, but the zygote does not develop.
Hybrid inviability: Hybrid embryo forms, but is not viable.
Hybrid sterility: Hybrid is viable, but the resulting adult is sterile.
Hybrid breakdown: First generation (F1) hybrids are viable and fertile, but further hybrid generations (F2 and backcrosses) are inviable or sterile.
An example of a postzygotic isolating mechanism. A mule is the offspring of a horse and a donkey. They are almost all sterile, except in very rare documented cases
Prezygotic mechanisms (Factors which prevent individuals from mating)
Temporal isolation- Individuals do not mate because they are active at different times. This may be different times of the day or different seasons. The species mating periods may not match up. Individuals do not encounter one another during either their mating periods, or at all.
Ecological, or habitat isolation: Individuals only mate in their preferred habitat. They do not encounter individuals of other species with different ecological preferences.
Behavioral isolation: Individuals of different species may meet, but one does not recognize any sexual cues that may be given. An individual chooses a member of its own species in most cases.
Mechanical isolation: Copulation may be attempted but transfer of sperm does not take place. The individuals may be incompatible due to size or morphology.
Gametic incompatibility: Sperm transfer takes place, but the egg is not fertilized.
Postzygotic isolating mechanisms
Genomic incompatibility, hybrid inviability or sterility.
Zygotic mortality: The egg is fertilized, but the zygote does not develop.
Hybrid inviability: Hybrid embryo forms, but is not viable.
Hybrid sterility: Hybrid is viable, but the resulting adult is sterile.
Hybrid breakdown: First generation (F1) hybrids are viable and fertile, but further hybrid generations (F2 and backcrosses) are inviable or sterile.
An example of a postzygotic isolating mechanism. A mule is the offspring of a horse and a donkey. They are almost all sterile, except in very rare documented cases
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For speciation to occur you need geographical barrier to separate them. Once they are separated the now can go through phylogenetic evolution which will make them now different species because they are in different places.