Dear student
Geographical isolation or reproductive isolation does not hold valid in asexual reproducing organisms because these organisms require single individual for reproduction and even if the organisms are separated geographically or are reproductively isolated they can reproduce by multiplication without creating significant variations.
Thus Speciation(formation of new species) in asexual reproducing organisms is very slow.
It can occur by various means or factors like
1.Natural selection-the process whereby organisms better adapted to their environment tend to survive and produce more offspring.
2.Mutation-sudden change in the structure of a gene.
3.Genetic drift-variation in the relative frequency of different genotypes in a small population
Regards