|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.