Final answer:
Hybrid individuals can have reduced fitness due to reinforcement, which leads to further divergence of parent species. If hybrids are more fit, species may merge, while stability describes the continuous but unchanged production of hybrids.
Step-by-step explanation:
Hybrids should have reduced fitness by a process known as reinforcement. Reinforcement occurs when hybrids are less fit than their parent species, leading to reduced hybrid reproduction over time and further divergence of the species.
However, if hybrids show equal or greater fitness, the two species may merge back into one. In some cases, species may remain separate but continue to produce hybrid individuals at stable rates, a situation referred to as stability, suggesting no significant change in the species' relationship.