Two species of tree frogs occupy different elevations in the canopy of a rain forest. If these frogs with strikingly different patterns of coloration but similar patterns of activity are brought together, they can produce offspring that survive to adulthood and can then mate successfully with individuals of either species. What keeps these frogs recognizably distinct?
1. Lack of hybrid fertility
2. Temporal isolation
3. Mechanical isolation
4. Habitat Isolation
5. Lack of hybrid viability