The Science of Pokémon: Regional Speciation
The Alola region, like other regions, is home to a unique floral and faunal pokémon. However, one aspect that is currently unique to Alola (seemingly) are Alolan regional variations of already well known pokémon. Differences between related pokémon as a whole is not new, like the two formes of Gastrodon (and Shellos). The East Sea and West Sea variations of Gastrodon are unique to the eastern and western portions of Unova respectively. Unlike Alolan formes, the two formes of Gastrodon are not different outside of their physical appearance. Both formes of Gastrodon have the same typing, states, moves, and abilities. This is not the case for Alolan formes, which is why they are so unique.
There are different types of speciation events that can result in various subspecies of organisms. In terms of Gastrodon, the two formes are a result of allopatric speciation. Allopatric speciation occurs when populations are separated geographically. For Gastrodon, they are geographically separated by Mt. Coronet, which splits Sinnoh in two. Once separated, the populations undergo genetic changes independently. If the populations do not merge back together, they may even become so different as that they will no longer be able to breed and produce viable offspring. Once this has occurred, the two subspecies are considered separate species. With Gastrodon, they can still breed, therefore they have not been geographically separated long enough to truly become two separate species. Alolan pokémon are similar in that regard. For example, an Alolan Muk can still breed with a standard Muk.
|The West Sea Gastrodon (pink and brown) and the East Sea Gastrodon (green and blue).|
|Muk (left) alongside Alolan Muk (right)|
Alolan pokémon, however, seem to have been isolated from their global counterparts longer than the two formes of Gastrodon. The morphological (size, shape, color, etc.) difference between the mainland subspecies and the island subspecies is very distinct. Often the differences go beyond simple appearances and extend to typing, abilities, and moves. Hypothetically, should the Alolan formes continue to be isolated from their mainland counterparts, they would eventually be different enough to constitute completely different pokémon species. It is possible that isolation events like these are what resulted in a lot of the morphologically similar rodent pokémon such as Pikachu, Emolga, Pachirisu, and Dedenne. These species can still breed, but they are distinctly different enough in morphology that the PokéDex considers them separate species. Like real world animals and plants, genetic work done on the electric rodents could potentially show that despite having very different morphological traits they are not true species, but rather subspecies (or in Pokémon World terms, formes) of the same species.