In which scenario can two species mate, yet the offspring cannot produce further offspring?

The scenario described is best represented by hybrid sterility. This occurs when two different species can mate and produce offspring, but those offspring are unable to reproduce themselves due to some form of infertility. A well-known example of hybrid sterility is the mule, which is the offspring of a horse and a donkey. Mules are generally healthy and viable but are sterile, meaning they cannot produce their own offspring.

In contrast, hybrid inviability occurs when the offspring do not survive to reach reproductive maturity, gamete isolation refers to the failure of sperm and egg to fuse in fertilization due to incompatibility, and behavioral isolation involves species having different mating behaviors or rituals that prevent them from mating in the first place. These terms highlight different aspects of reproductive barriers between species, but they do not specifically address the scenario where offspring are produced but are not fertile.