As I think is documented in the Sidle docs (and if not I will add it): tree reconstruction only works for databases that have SEPP reference trees. This means you can reconstruct using Silva 128 or Greengenes 13_8 if you want a tree. If you'd like to build the backbone for fragment insertion with another database or database version, you're able to do that. I don't think there's a clean solution at the moment; the last thread i can find on building is from last year.
