Molecular Underpinnings of Speciation

An egg cell has a nucleus and organelles like the Golgi body and mitochondria. A sperm cell only has a nucleus on the inside. When the egg is fertilized by a sperm from a different species, the genetic information contained in the mitochondria, which is always inherited from the mother, can have harmful interactions with the genes from the father. This can cause the development of the zygote to stop. What kind of reproductive isolation is this?