Reproductive Isolating Mechanisms
Reproductive Isolating Mechanisms
Any heritable feature of body form, function, or behavior that prevents interbreeding between one or more genetically divergent populations Results as a by-product of genetic divergence Maintains positive adaptations for specific environments 1. Prezygotic Isolating Mechanisms 2. Postzygotic Isolating Mechanisms
Hybrid Inviability
Egg of one species is fertilized by sperm from another species, but fertilized egg cannot develop past early embryonic stages
Gametic Isolation
Incompatibility gametes of different species are incompatible at the molecular level resulting in mortality
Ethological Isolation
Isolated by behaviors Copulation proceeded by courtship displays Reciprocity produces sexual stimulation Ex: Birds, some can not recognize the mating signals of other birds
Geographic Isolation
Isolated by distance or geographic barriers (Do not come in contact) Distance or barrier relative to the size of the organisms Ex: Head lice and body lice Geographic isolation is the hairless region of the neck
Mechanical Isolation
Isolated by incompatible reproductive part size or shape Mechanical isolation is often severe, wrong mating types can result in mortality to both males and females "Key doesn't fit the whole"
Temporal Isolation
Isolated by reproductive events that occur at different times (mating, flowering days or seasons do not overlap) Ex: Cicadas
Ecological Isolation
Isolation due to adaptation to different microclimates in the same habitat Ex: California Oaks - 3 species Separation is based on physiological mechanisms to promote conservation of water
Postzygotic Isolating mechanisms
Mechanisms of isolation after fertilization 1.Zygotic Wastage 2. Hybrid Sterility 3. Hybrid Inviability 4. Hybrid Breakdown
Prezygotic Isolating Mechanisms
Mechanisms of isolation before or during fertilization 1.Ecological Isolation 2. Geographic Isolation 3. Temporal Isolation 4. Ethological Isolation 5. Mechanical Isolation 6. Gamete Isolation
Zygotic Wastage
Minimum # of zygotes required per species to achieve a viable adult
Hybrid Sterility
No viable sperm or egg
Hybrid Breakdown
Offspring fertile but their offspring are sterile or have genetic abnormalities (hybrids have low fitness)
Gametic Wastage
minimum # of sperm required per species to achieve fertilization