I have Qiime2-derived taxa data. I have converted the taxa data to relative abundance per sample. Given that I have three sample groups, can I use any statistical test methods like Kruskal-Wallis test followed by posthoc analysis for finding the statistically significant taxa between the sample groups?
You can use some of the Differential abundance (DA) analysis methods to obtain the statistical difference between your groups. Depending on your dataset, you can use for example LEfSe (although it hasn't been already working for a few months), ANCOM, ANCOM-BC (these two are a part of QIIME2) or DESeq2.