Just last month, a bunch of Hoenn Pokémon were introduced into Pokémon GO, but it already looks like some changes are being made. Like with previous Generations, the Third Generation of Pokémon in the game contains a few that are region-specific, meaning you can only catch them in certain areas of the world. For example, Farfetch’d can only be caught in Asia, while Tauros can only be caught in North America.
With the first big Hoenn update in Pokémon GO, Zangoose was added as a Pokémon exclusive to Africa, North America and South America, while Seviper was exclusive to Europe, Asia and Oceania. However, according to Serebii, it would seem that the two have recently switched places, with Zangoose now being exclusive to Europe, Asia and Oceania and Seviper exclusive to Africa, North America and South America. It is unknown how long this change will last before the two Pokémon switch back, or if they will switch back at all.
Other new region-specific Pokémon include Plusle, only available in Africa, North America and South America, and Minun, only available in Europe, Asia and Oceania, as well as Relicanth, which can only be found in the waters of and around New Zealand and nearby islands. There is no word about Plusle and Minun switching places or other future instances of region-specific Pokémon becoming available outside their natural habitats.