A major difference between allopatric and sympatric speciation is whether resulting species are reproductively isolated or not. gene flow continues...

A major difference between allopatric and sympatric speciation is whether

resulting species are reproductively isolated or not.

gene flow continues to occur or not.

two or three species result.

geographic isolation is required or not.

the new species are separated by a prezygotic or postzygotic isolating mechanism.