Hi @LVC,
ANCOM will not "assign" these to any group. When you have more than 2 groups, it can be difficult to interpret which group is associated with any differentially abundant features, and you have two options:
- look at the abundances of those features in each group to "eyeball" which group(s) most likely have different abundances of that feature
- if you really must, run a post-hoc test (which in this case would be running ANCOM on each pair of groups)
The percentile abundance table is sort of inconvenient but should give you an idea which group(s) that feature is more abundant in. Another (more useful?) option: filter your feature table to contain only the significant features and plot as a heatmap with qiime feature-table heatmap.
Good luck!