I have been attempting to create a 16S rRNA analysis pipeline that uses de novo otu picking, using mostly Qiime. The pipeline that I am using does not ever output the actual Greengenes identifiers that are referenced when assigning taxonomy to my otus that are defined. Is this standard in de novo otu picking? For some functional as well as some tree creation, I would need those Greengenes identifiers, so does this mean that to do analyses, such as PICRUSt, that I would have to do an open reference otu picking method?