[Jewbacca]

I had to get my English dictionary:

“allopatric speciation”-— Speciation that depends on an external barrier to gene flow (such as geographic isolation) to begin or complete the process of speciation.

Is the concept being discussed.

Foster’s Rule is the first step in allopatric speciation.

[TheThirdRuffian]

“allopatric speciation” -— a much more eloquent statement of my hypothesis.