A genetic isolate is population of organisms that has little genetic mixing with other organisms within the same species. This may result in speciation, but this is not necessarily the case. Genetic isolates may form new species in several ways:

• allopatric speciation, in which two populations of the same species are geographically isolated from one another by an extrinsic barrier, and evolve intrinsic (genetic) reproductive isolation
• peripatric speciation, in which a small group of a population is separated from the main population, and experiences genetic drift
• parapatric speciation, in which zones of two diverging populations are separate, but do overlap somewhat; partial separation is afforded by geography, so individuals of each species may come in contact from time to time, but selection for specific behaviours or mechanisms may prevent breeding between the two groups.
• sympatric speciation, a contentious method of speciation in which species diverge while inhabiting the same place.