Grouping 16s data based on treatment to do alpha diversity between groups

Hi all,
I am a new user in usegalaxy website. I have followed " 16S Microbial Analysis with mothur (extended)" and it was so interesting.
My Q is: if I have a data of 16srRNA for a number of samples divided to 3 groups: treated, untreated and control, how can I do this division on the data to do alpha analysis between groups and to know if there is a significant difference between these groups or not.
A second Q plz, I have 16s data analyzed by Qiime till the alpha diversity point but each sample in individual and I have all the generated files of OTU fasta and BIOM, can I load any of this files to Galaxy to be grouped as described previously and analyzed them based on the treatment.