Postzygotic barrier

Definition

A postzygotic barrier is a reproductive mechanism that occurs after fertilization, preventing the hybrid offspring from developing into viable, fertile adults. These barriers act to reduce gene flow between different species, thus promoting speciation by ensuring that even if fertilization occurs, the resulting hybrids are less likely to survive or reproduce successfully.

5 Must Know Facts For Your Next Test

1. Postzygotic barriers can take several forms, including hybrid inviability, hybrid sterility, and hybrid breakdown, each affecting the viability and reproductive success of hybrids differently.
2. One well-known example of a postzygotic barrier is the mule, which results from mating between a horse and a donkey. Mules are generally sterile and cannot reproduce, demonstrating hybrid sterility.
3. These barriers contribute to the process of speciation by ensuring that even if two species mate and produce offspring, the hybrids may not thrive or reproduce, thus maintaining species boundaries.
4. Postzygotic barriers often arise due to genetic incompatibilities that lead to developmental issues or fitness disadvantages in the hybrid offspring.
5. The study of postzygotic barriers helps scientists understand how reproductive isolation can lead to biodiversity and the formation of new species over time.

Review Questions

• How do postzygotic barriers contribute to the process of speciation?
  • Postzygotic barriers play a crucial role in speciation by reducing gene flow between species after fertilization occurs. By preventing hybrid offspring from developing into viable and fertile adults, these barriers help maintain the distinctiveness of species. This reproductive isolation allows populations to diverge genetically over time, leading to the emergence of new species.
• Compare and contrast postzygotic barriers with prezygotic barriers in terms of their mechanisms and effects on speciation.
  • Postzygotic barriers occur after fertilization and prevent hybrid offspring from surviving or reproducing successfully, while prezygotic barriers act before fertilization to prevent mating or fertilization between species. Both types of barriers serve to reduce gene flow between populations, but they function at different stages of reproduction. Understanding both mechanisms is essential for comprehending how speciation occurs and how reproductive isolation is established.
• Evaluate the significance of hybrid inviability and hybrid sterility as types of postzygotic barriers in maintaining biodiversity.
  • Hybrid inviability and hybrid sterility are significant types of postzygotic barriers that help maintain biodiversity by limiting the successful reproduction of hybrids. Hybrid inviability leads to the death or poor development of hybrid offspring, while hybrid sterility prevents hybrids from reproducing altogether, as seen in mules. By ensuring that hybrids do not contribute to the gene pool of parent species, these barriers support the continuation of distinct species and promote evolutionary divergence, thereby enhancing overall biodiversity in ecosystems.

Related terms

prezygotic barrier:

A prezygotic barrier is a reproductive mechanism that prevents fertilization from occurring between different species, such as temporal isolation or habitat isolation.

hybrid inviability: Hybrid inviability is a specific type of postzygotic barrier where the hybrid offspring fail to develop properly or die before reaching reproductive maturity.

speciation:

Speciation is the evolutionary process by which populations evolve to become distinct species, often involving mechanisms like postzygotic and prezygotic barriers.