Final answer:
Speciation occurs through geographic separation or mechanisms within a shared habitat, with reproductive isolation acting as a barrier between closely related species. In hybrid zones, species evolution may take the pathways of stability, fusion, or reinforcement.
Step-by-step explanation:
Speciation occurs along two main pathways: geographic separation (allopatric speciation) and through mechanisms that occur within a shared habitat (sympatric speciation). Both pathways isolate a population reproductively in some form. Mechanisms of reproductive isolation act as barriers between closely related species, enabling them to diverge and exist as genetically independent species.
One example of speciation is allopatric speciation, which involves a geographic separation of populations from a parent species and subsequent evolution. Another example is sympatric speciation, where speciation occurs within a parent species while remaining in one location.
In hybrid zones, three pathways of species evolution may occur: stability, fusion, and reinforcement. Stability refers to the two species continuing to exist as separate species without much genetic exchange. Fusion refers to the two species merging back into one due to ongoing hybridization. Reinforcement refers to the strengthening of reproductive barriers between the two species to prevent further hybridization.