With asexually reproducing species, individuals are grouped by morphology and biochemistry. The educated guess. Determine the amount of difference between overlapping species. Determine the amount of difference between separated specie. If is less than the control they are the same if it is more than the control, they are not 4.
Species maintain their integrity when they consistently choose mates with in their species.
Due to natural selection pressure and sexual selection pressure, the alleles which survive in the new population are most likely to be neutral alleles. Hence, the populations hold their identity even with gene flow. Because it has a different genetic make up and is under different natural selection pressure, over time it will differentiate from the original population to and extent that results in reproductive isolation. Three out comes when isolated populations are reunited 1. Habitat isolation 2.