Final answer:
In a hybrid zone, two closely related species may reproduce along with interacting, leading to the formation of hybrid offspring. The fitness of these hybrids determines whether reinforcement, fusion, or stability occurs in the hybrid zone.
Step-by-step explanation:
In a hybrid zone, two closely related species may reproduce along with interacting. This means that hybrid offspring of two closely related individuals are produced in the hybrid zone, which is an area where two closely related species continue to interact and reproduce, forming hybrids.
Hybrids can be less fit, more fit, or about the same fitness level as their parents. If the hybrids are less fit, the two species may continue to diverge in a process called reinforcement. If the hybrids are as fit or more fit than the parents, the two species may fuse back into one species. Sometimes, two species can remain separate but continue to interact to produce hybrid individuals, which is classified as stability.