PERMANOVA results significant, but differential abundance results detect 0 significantly different ASVs

[salias (Sergio Alías-Segura)]

Hello @PabloCL

@PabloCL

I am wondering if it is possible that there is a significant global difference between two communities without any given ASV being the cause for that difference.

I think this could make sense. Your significant PERMANOVA result could be explained by small and consistent changes in the abundance of many different ASVs. None of these would be large enough to be statistically significant on their own.

Another possible explanation could be dispersion. PERMANOVA is sensitive both to intergroup variance and dispersion. In this regard, I found this post really useful: adonis, betadiver, and betadisp

@PabloCL

Performing DA analysis at aggregated higher taxonomic levels gives similar results, with no taxa being differentially abundant.

If you don’t find DA ASVs, I wouldn’t expect to find DA species or genera. In my experience, the more you collapse by taxa, the fewer DA features you find (they tend to “cancel” each other when you aggregate).

Best,

Sergio