About yggdrasil

I've been playing all the remakes of dq 3, 1, and 2 and I have a question about yggdrasil. How did it get from the overworld in the first part of dq3 to the "underworld" Alefgard as the overworld of dq3 is after dq11 right? So how did yggdrasil move from one world to another or is it more of every world has a yggdrasil and a different history behind it I havent played all the games in the series so maybe I just need to play the rest of the games to get more lore but this just confused me while I was playing dq2 thinking back to 11.