According to James Jacobs, the Wyrdwoods can't be found in Golarion. In fact, most of the playable races found in Bestiary 4 (which originally appeared in Advanced Races Guide) are quite alien to the setting for some players.
In my personal opinion, I think most of those races should be located in Nex, even the Wyrdwoods. However I would like to know in which planets of the Golarion solar system you would located them?
I am not so sure James Jacob meant to say "These don't exist on Golarion" as in "We do not yet have a place for them or have figured out there role"
We do know about 1 of the 5 races though: Kasatha are found in Numeria and apparently originated outside the solar system.
Well, I'd plunk wyrdwoods into some of the ancient forests that either used to be elven strongholds or that touch the First World, maybe even on Castrovel. I'd refluff them to be created by non-humanoid sylvan races -- treants and elder dryads -- from naturally-fallen trees to act as their agents (and soldiers when necessary) among the common humanoid races. Perhaps an ancient elder aspen grove on Castrovel is slowly creating them as an eventual army to interplanetary teleport into Kyonin, reclaim the Tanglebriar, and drive Treerazer back into the Abyss?
Incorporating what little information is cannon (based on Bestiary 4), I would put the remaining races in these places:
Gathlain: Arcadia? For some reason they feel like they could fit well there
Trox: They escaped from Duergar control to the surface, where they are still in danger of enslavement. I would have most of the population still be down in the Darklands, but maybe have a few isolated tribes in the Hold of Belkzen or Five King Mountain regions, and perhaps other regions with a strong Darklands immigrant population
Wyrwood: Castrovel. Someone in the James Jacob thread wonder if there was an elvish connection, since elves use that type of wood in construction.
At any rate, Castrovel needs more races, and I could see a cabal of Wyrwood actively fighting against the elves
Wyvaran: Triaxus. I see them as serving as troops amongst the Drakelands Dragons. Given that a major theme of Triaxus is "Dragons", it seems like their should be a medium draconic race there