In the previous section we discussed the concept of species in detail and concluded that the concept of biological species and Mayr's definition of species have a wide acceptance among biologists. In this section we shall proceed to discuss the mechanisms of speciation or the mode of formation of a species. Mayr's definition of species amply makes it clear that to qualify for the title of the species, the individuals must be reproductively isolated from other groups. This naturally raises a question whether a new species could arise from populations occupying the same territory. In other words, should the populations of parent species live in quite separate territories in the formation of new species? In our earlier discussions. on natural selection, you have learnt that originmof adaptations is a gradual process, This is much more true of speciation. Biologists recognise three different kinds of speciation.