What Is Alopatric Speziation?

In order to have two different species, they have to be genetically isolated from each other. The most common genetic mechanism for that is polyploidy or heteroploidy. One Patrick's speciation is when one population becomes two species in the same physical space. This is like a sicklid fish event through homoploid sympatric speciation. I think that happens typically... These are very closely related but look very different even though they might be similar.