What describes hybrid sterility?

Hybrid sterility refers to a situation where a hybrid organism—an offspring resulting from the mating of two different species—reaches maturity but is incapable of reproducing successfully. This phenomenon often occurs in post-zygotic reproductive barriers, where the genetic differences between the parent species lead to reproductive isolation even after fertilization.

In this case, the hybrid may be fully formed and functional but may possess chromosomal or genetic abnormalities that prevent the formation of viable gametes, which are necessary for reproduction. An example of this can be seen in mules, which are hybrids of horses and donkeys; mules are typically sterile and cannot produce offspring.

Understanding hybrid sterility is critical in the study of speciation as it highlights how reproductive barriers contribute to the maintenance of species boundaries, thus influencing the evolutionary process.