Speciation is an evolutionary process which explains how a new plant or animal species is created. Allopatric speciation is a type of speciation in which two population of the same species become geographically isolated. The geographically isolated species can no longer interbreed, so they become two different species.
Types of Allopatric Speciation
Biologists divide allopatric speciation into two types viz., dispersal and vicariance. In dispersal, a few members of a species move to a new geographical area where they face new environment so they behave differently and by the passage of time many new genetic mutations lead to the formation of a different species. Hence, in vicariance species become isolated from each other by a natural situation such as mountain formation or island formation etc.
How Allopatric speciation takes place?
Allopatric speciation can take place in a variety of ways. The isolation of the populations can take place by a physical barrier such as a mountain range or a waterway. So each isolated population undergoes different selective pressures, different gene mutations occur and accumulate. These mutations lead to different characteristics between those populations. Many beneficial genetic mutations build up and these changes gradually lead to the rise of a new species.
In this way, the two populations become so distinct that they can no longer breed with each other. In this way, two different species arise by they process of allopatric speciation.
Examples of Allopatric Speciation
Darwin’s finches or Galapagos finches are a good example of allopatric speciation. Darwin discovered fifteen different species of finches at the Galapagos Islands. These finches were different from each other on the basis of the shape and size of their beaks. Their beaks were specialized for the type of food each of them eats, from parrotlike fruit eating beaks to crushing beaks for eating seeds. Other variants are grasping bills and probing bills.They shape of their beaks range from the large blunt beaks to long thin beaks.
All of these species came from a common ancestor that probably have been emigrated to different islands. Once they established themselves to the new environments of different islands they become isolated from each other. Different mutations arose in these populations simultaneously which made them successful in their new habitats. These beneficial mutations became more and more prevalent and lead to the formation of new species. When new species arise from a common ancestor due to geographical isolation it is called allopatric speciation.
Other examples include Grand Canyon Squirrels, Northern and Mexican Spotted Owls.