Which of the following can result in speciation from bio geographic isolation

The effect of geographic isolation is that the two populations are subjected to different selection (pressures) and geographic conditions. The conditions in the two areas, if different, will produce different alleles in that species and will be selected for, where genetic differences will gradually accumulate between the two different populations.

In time, enough genetic differences will occur so that the two populations will no longer interbreed. Then, by definition, they have become different species.