Question

When members of a species become separated by geography and lose the ability to interbreed, how would scientists classify them?

Answer 1

Scientists would classify them as being in the same genus perhaps, but they would no longer be part of the same species. 

Answer 2

allopatric speciation

Step-by-step explanation:

In any form of speciation, population of a species is divided into parts or groups due to the presence of any barrier up to an extent that it cannot mate with each other. In case where these barriers are geographical barriers then it is known as allotropic speciation.

Being isolated from each other, the two species evolve separately. In case if after certain period of time the two separated populations are put together, even then there occurs no mating between them.