Allopatric Speciation
- Allopatric speciation occurs as a result of geographical isolation
- It is the most common type of speciation
- A species population splits into one or more groups which then become separated from each other by geographical barriers
- The barrier could be natural like a body of water, or a mountain range
- It can also be man made (like a freeway)
- This separation creates two populations of the same species who are isolated from each other, and as a result, no genetic exchange can occur between them
- If there is sufficient selection pressure or genetic drift acting to change the gene pools within both populations then eventually these populations will diverge and form separate species
- The changes in the alleles/genes of each population will affect the phenotypes present in both populations
- Over time, the two populations may begin to differ physiologically, behaviorally and morphologically (structurally)
Example of Allopatric Speciation in Trees
- Imagine there is a population of trees that are all one species
- A new mountain range forms that divides the population into two
- The natural barrier prevents the two groups from interbreeding, so there is no gene flow between them
- The two populations experience different selection pressures and genetic drift
- Over thousands of years the divided populations form two distinct species that can no longer interbreed
Allopatric Speciation Example Diagram
The natural geographical barrier of a mountain range can lead to allopatric speciation in trees
Other Examples of Allopatric Speciation
- Hawaiian Drosophila
- Two distinct species of fruit fly of the genus Drosophila have emerged by allopatric speciation on different islands of the Hawaiian archipelago
- Drosophila silvestris inhabits Hawai’i Island and Drosophila planitibia inhabits the island of Maui
- Caribbean Anolis
- These are anole lizards of the genus Anolis
- They have speciated from one colonizing species to around 150 distinct species via reproductive and geographical isolation, over millions of years